Как пишется джипиэс на английском языке

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• 1
  GPS
  
  

  GPS, general-purpose shelter

  ————————

  GPS, global-positioning satellite (system)

  ————————

  GPS, global-positioning system

  ————————

  GPS, ground positioning system

  ————————

  GPS, guidance power supply

  ————————

  GPS, gun position sensor

  ————————

  GPS, gunner’s primary sight

  абт основной прицел (башенного) стрелка

  English-Russian dictionary of planing, cross-planing and slotting machines > GPS

• 2
  GPS
  
  

  English-Russian dictionary of modern abbreviations > GPS

• 3
  GPS
  
  

  GPS, global positioning system

  English-Russian dictionary of program «Mir-Shuttle» > GPS

• 4
  GPS
  
  

  1. универсальная система
  2. система глобального позиционирования
  3. глобальная система позиционирования (источник синхронизации времени)
  4. глобальная навигационная система

  глобальная навигационная система
  (прежнее название — Navstar)
  В эксплуатацию введена в 1995 г., обслуживание осуществляет МО CША. GPS предназначена для передачи навигациенных сигналов, которые могут быть одновременно приняты неограниченным количеством пользователей, находящихся в различных регионах мира. Создаваемая как система военного применения, в настоящее время GPS широко используется во всем мире для решения гражданских задач (отслеживание местоположения на море, суше и в воздухе). С помощью GR-приемника определяются координаты объекта (широта и долгота), скорость движения и темное время (табл. G-3). См. A-CPS, ODGPS, DGPS.
  [Л.М. Невдяев. Телекоммуникационные технологии. Англо-русский толковый словарь-справочник. Под редакцией Ю.М. Горностаева. Москва, 2002]

  Тематики

  • электросвязь, основные понятия

  EN

  • GPS
  • Global Positioning System

  система глобального позиционирования
  СГП
  Навигационная спутниковая система, обеспечивающая пользователей информацией о месте нахождения, скорости и времени в любой точке Земли. Система использует навигационные спутники. При проектировании системы планировалось вывести 24 спутника на квази стационарные орбиты. Такие системы обеспечивают круглосуточную информацию о трехмерном положении, скорости и времени для пользователей, обладающих соответствующим оборудованием и находящихся на или вблизи земной поверхности (а иногда и вне её). Первой системой GPS, широко доступной гражданским пользователям, стала NAVSTAR, обслуживаемая Министерством обороны США.
  [ http://www.morepc.ru/dict/]
  
  система глобального позиционирования
  GPS представляет собой спутниковую технологию позиционирования, которая позволяет при помощи GPS-приемника определять свои координаты в любой точке мира. Приемники GPS производятся в виде наладонных устройств, навигационных систем для автомобилей, а также модулей, устанавливаемых в карманные ПК (PDA), например, PalmPilot.
  [ http://www.sotovik.ru/lib/news_article/news_26322.html]

  Тематики

  • информационные технологии в целом

  EN

  • Global Positioning System
  • GPS

  Англо-русский словарь нормативно-технической терминологии > GPS

• 5
  GPS
  
  

  English-Russian electronics dictionary > GPS

• 6
  GPS
  
  

  The New English-Russian Dictionary of Radio-electronics > GPS

• 7
  GPS
  
  

  [lang name=»English»]Global Positioning System, GPS

  созданная министерством обороны США система глобальной навигации на основе группировки из 24-х спутников, движущихся по орбитам высотой 20200 км; принимая сигналы от нескольких спутников, приемник GPS способен с высокой точностью определять плановые и высотные координаты любой точки на и вблизи поверхности Земли

  The English-Russian dictionary of geoinformatics > GPS

• 8
  GPS
  
  

  тех. сокр.

  Система глобальной навигации, глобальная система определения местоположения, система спутниковой навигации, спутниковая навигационная система, спутниковая система позиционирования, глобальная система местоопределения.

  В данной системе глобального позиционирования, применяются низколетящие орбитальные спутники, помогающие определить место положения на поверхности земли с высокой точностью до 15-45 метров. Данная система применяется туристами, путешественниками, рыболовами и многими другими кому нужно средство ориентации на местности такой точности.

  Базируется на считывании информации со спутников системы GPS по «гражданскому» (открытому) каналу и вычисления x, y и z — координат (широты, долготы и высоты над уровнем моря), скорости и некоторых других параметров процессором приемника.

  Англо-русский универсальный дополнительный практический переводческий словарь И. Мостицкого > GPS

• 9
  GPS
  
  

  I

  general problem solver

  II

  Global Position System

  GPS система, глобальная система навигации и местоопределения

  III

  general-purpose system

  English-Russian dictionary of computer science and programming > GPS

• 10
  GPS
  
  

  I

  2) — Универсальный решатель задач, [программная] система

  II

  Англо-русский толковый словарь терминов и сокращений по ВТ, Интернету и программированию. > GPS

• 11
  GPS
  
  

  Оборудование

  Global Positioning System
  Система Глобального Позиционирования
  Набор постоянно движущихся спутников (находящихся на шести орбитах на высоте примерно 17000 км над поверхностью Земли) и наземных станций, предназначенный для точного определения координат местоположения человека (а точнее, находящегося у человека GPS-навигатора).
  Данная система была введена в действие США в 1994 году.

  English-Russian dictionary of computer abbreviations and terms > GPS

• 12
  GPS
  
  

  Большой англо-русский и русско-английский словарь > GPS

• 13
  GPS
  
  

  Англо-русский словарь технических терминов > GPS

• 14
  gps
  
  

  I gallons per second

  II grams per second

  Англо-русский словарь технических терминов > gps

• 15
  GPS
  
  

  English-Russian dictionary of geology > GPS

• 16
  GPS
  
  

  * * *

  сокр.

  галлонов в секунду

  * * *

  Англо-русский словарь нефтегазовой промышленности > GPS

• 17
  GPS
  
  

  3) Военный термин: Geographical Positioning System, Grid Producing Source, Ground Processing Stations, Gunners Primary Sight, general-purpose shelter, global-positioning satellite, ground positioning system, guidance power supply, gun position sensor, глобальная система навигации и определения местоположения, глобальная система определения координат

  10) Сокращение: Global Position System , Global Positioning Satellite, Global Protection System, Ground Playback Station, Gunner’s Primary Sight, gallon per second, general problem solver, general purpose submarine, геометрические характеристики изделия

  19) Глоссарий компании Сахалин Энерджи: ground positioning satellite , геодезический спутник , определение положения на местности с помощью искусственного спутника , Global Positioning System , Добыча и Реализация Газа

  31) NYSE. The Gap, Inc.

  Универсальный англо-русский словарь > GPS

• 18
  gps
  
  

  3) Военный термин: Geographical Positioning System, Grid Producing Source, Ground Processing Stations, Gunners Primary Sight, general-purpose shelter, global-positioning satellite, ground positioning system, guidance power supply, gun position sensor, глобальная система навигации и определения местоположения, глобальная система определения координат

  10) Сокращение: Global Position System , Global Positioning Satellite, Global Protection System, Ground Playback Station, Gunner’s Primary Sight, gallon per second, general problem solver, general purpose submarine, геометрические характеристики изделия

  19) Глоссарий компании Сахалин Энерджи: ground positioning satellite , геодезический спутник , определение положения на местности с помощью искусственного спутника , Global Positioning System , Добыча и Реализация Газа

  31) NYSE. The Gap, Inc.

  Универсальный англо-русский словарь > gps

• 19
  GPS
  
  

  <06>

  мировая спутниковая позиционная система

  Сборный англо-русский словарь > GPS

• 20
  GPS
  
  

  Терминологический словарь МИД России > GPS

джипиэс — перевод на английский

Показать ещё примеры для «gps»…

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Перевод «ДжиПиЭс» на английский

Спенсер нанял для него машину, вбил адрес в ДжиПиЭс.

Spenser rented him a car, plugged the address into the GPS.

Они отключили ДжиПиЭс. А коды безопасности могли использоваться дюжинами наших сотрудников.

They disabled the GPS, and the security codes could have been used by dozens of our employees.

Мы сели на поле, ДжиПиЭс вышла из строя.

We’ve set down in a field, GPS malfunctioned.

Значит, ему нельзя покидать Иллинойс, отследили ДжиПиЭс на машине.

And he wasn’t supposed to leave Illinois, but I ran GPS on his car.

В ДжиПиЭс мой домашний адрес значится как «Дакриб», потому что мы живем на улице Дакриб.

My home address is in the gps under «dacrib» ’cause we live on dacrib avenue.

Она найдет Майлза, а вот мы никогда не найдем ее, во всяком случае без ДжиПиЭс точно.

She will find Miles, but we will never find her, not without a GPS.

Я должен подключить Джипиэс или…?

Should I plug it into the GPS, or…?

Если кто-то украл у меня джипиэс, маршрут привел его прямиком к Доаксу.

If someone stole my GPS it would have let them straight to Doakes.

Водитель не берёт трубку, так что мы отслеживаем его по ДжиПиЭс.

Driver won’t answer his phone, so we’re pinging his GPS unit.

У неё на мобильном стоит ДжиПиЭс маяк.

We’ve got GPS tracking on her mobile phone.

Я уже давно слежу за Смурф по ДжиПиЭс.

I’ve had the GPS on Smurf for a while.

ДжиПиЭс на мобильниках показывает, что Луиза и Виктория были вместе вчера вечером и сегодня утром.

Cell G.P.S. put Louise and Victoria together last night and again this morning.

Если на вашем телефоне отключена функция ДжиПиЭс, мы попытаемся засечь треугольник, в котором вы находитесь.

Sir, if your phone’s GPS capability has been disabled, we’re going to have to triangulate your position through the cell towers to pinpoint your location.

Телефон Бена был отключен во время нападений, по ДжиПиЭс ничего, звонков

Ben’s phone was off during the hits so we got no GPS, no calls or texts to link to the robbery.

Другие результаты

Декстер, я проверила, Джипиэса в минивэне нет.

По джипиэсу срабатывает? З года назад

После прочтения книги Галтон наследственности Джиниэса (1869) Чарльз Дарвин написал ему сказал

After reading Galton’s book Hereditary Genius (1869) Charles Darwin wrote to him saying

В 1869 в наследственности Джиниэса‘, он стремился доказать, что гений является главным вопросом происхождения, и он следует, что с многих других книг и документов по различным аспектам этой темы.

In 1869, in ‘Hereditary Genius‘, he endeavoured to prove that genius is mainly a matter of ancestry, and he followed that up with many other books and papers on various aspects of the subject.

Ничего не найдено для этого значения.

Результатов: 18. Точных совпадений: 14. Затраченное время: 74 мс

Documents

Корпоративные решения

Спряжение

Синонимы

Корректор

Справка и о нас

Индекс слова: 1-300, 301-600, 601-900

Индекс выражения: 1-400, 401-800, 801-1200

Индекс фразы: 1-400, 401-800, 801-1200

Примеры:

Гпс (примеров 110)

A Global Positioning System (hereinafter «GPS«);	А..2.1.3 глобальная система позиционирования (здесь и далее «ГПС«);
The distance indicated by the vehicle odometer shall be checked against the GPS data and verified.	Пробег, снятый со счетчика пробега транспортного средства, сравнивают с данными ГПС и проверяют.
Those coordination activities were essential to maintain open markets and to ensure the global acceptance of GPS.	Такая координационная деятельность имеет важнейшее значение для поддержания открытых рынков и обеспечения глобального принятия ГПС.
Implementation of six GPS courses for civilian staff and 9 GPS training visits for military team sites	Проведение 6 занятий по обучению пользованию приемниками ГПС для гражданских сотрудников и 9 учебных выездов в опорные пункты для военного персонала
The Bureau of Indian Affairs continued to conduct natural resource inventories, image mapping projects, and GPS training services to support its Indian Integrated Resource Information Program.	Бюро по делам индейцев продолжало проводить инвентаризацию природных ресурсов, осуществлять проекты по картированию местности с помощью спутниковых изображений и готовить кадры по ГПС в целях оказания поддержки Программе комплексного учета информации о ресурсах индейских резерваций.

Больше примеров…

Гсок (примеров 53)

Information technologies, including GIS, remote sensing and GPS, offer valuable technologies for land planning and management.	Информационные технологии, включая ГИС, дистанционное зондирование и ГСОК, представляют собой ценные технологические средства, необходимые для обеспечения планирования и рационального использования земельных ресурсов.
The increasing use of hand-held devices with GPS and low-cost aerial and satellite imagery for spatial data collection and the demarcation of statistical enumeration areas, as well as geographic information systems for the display of census information, have improved census mapping in fundamental ways.	Все большее применение портативных устройств с ГСОК и получение недорогостоящих изображений с воздуха и со спутников в целях сбора пространственных данных и демаркации районов статистических обследований, а также геоинформационные системы для отображения информации переписи кардинально улучшили картирование в рамках проведения переписей.
Information technologies, including Internet access, GIS, remote sensing and GPS offer valuable technologies for SARD.	Информационные технологии, в том числе доступ к Интернет, ГИС, дистанционное зондирование и ГСОК, таят в себе ценные технологии устойчивого ведения сельского хозяйства и развития сельских районов.
Locations of continuous GPS observation were proposed for the collection of precise crustal deformation data.	Для сбора точных данных о деформации земной коры было предложено в ряде мест организовать непрерывное наблюдение с использованием ГСОК.
In June 2002, the Motor Car Amendment Act made the GPS system mandatory for taxis with a grace period of 18 months for installation.	В июне 2002 года указом о поправке к закону об автотранспортных средствах ГСОК была признана обязательной для такси и был предусмотрен 18-месячный срок для ее установки27.

Больше примеров…

Навигатор (примеров 34)

My internal GPS has been recalculating for a week.	Мой внутренний навигатор производил пересчёт неделю.
It’s likely the GPS gave Van Pelt bad directions.	Похоже навигатор указал Ван Пелт неправильное направление.
Gps says were 5 minutes away.	Навигатор сказал ехать еще 5 минут.
You know you have a GPS tracker on your cruiser.	Ты в курсе, что у тебя навигатор с обратной связью?
Okay, well, the GPS in the family car has been disabled, so they’re definitely in the wind.	Навигатор в машине отключен, так что они явно в бегах.

Больше примеров…

Координаты (примеров 47)

I need you to get the GPS coordinates for the metadata.	Нужно узнать координаты из метаданных.
The use of global positioning system was not retained as the GPS position is not always available on site.	Использование для этого координат системы спутниковой навигации поддержано не было, поскольку такие координаты не всегда можно установить на месте происшествия.
I’m sending you a postcode and my GPS.	Высылаю код и мои координаты.
1 Fix quality (0 = invalid, 1 = GPS fix, 2 = DGPS fix (This field can have any valid value.)	1 Свойства координаты (0 = недействительно, 1 = координата ГПС, 2 = координата ДГПС. (В этом поле может указываться любое действительное значение.)
So with the help of some biologists studying the fungus, I got some maps and some GPS coordinates and chartered a plane and started looking for the death rings, the circular patterns in which the fungus kills the trees.	Итак, с помощью биологов, изучающих грибки, я получила карты, координаты Джи Пи Эс, заказала билет на самолёт и стала искать смертельные круги, округлые структуры, которыми грибок убивает деревья.

Больше примеров…

Джи-пи-эс (примеров 17)

I’m tracking you through the GPS in Shaw’s phone.	Я слежу за тобой через Джи-Пи-Эс телефона Шо.
In a moving canister with no phone and no GPS, because the only window is sealed shut.	В передвижной канистре без телефона и Джи-Пи-Эс, потому что единственное окно замуровано.
And the GPS is on the fritz.	К тому же джи-пи-эс снова сломался.
It had a hidden GPS.	Там был датчик джи-пи-эс.
What, that’s someone else’s GPS.	Это точно не мой Джи-Пи-Эс.

Больше примеров…

Гсм (примеров 14)

In conclusion there is no particular experience with GPS in rail freight in Hungary for the time being.	На данный момент ГСМ в секторе железнодорожных перевозок в Венгрии практически не используется.
The use of tools, such as environmental indicators, checklists, impact matrices, GIS, GPS and satellite images, will also be explored.	Также будет изучена возможность использования таких средств, как экологические показатели, перечни контрольных параметров, матрицы воздействия, ГИС, ГСМ и спутниковые изображения.
Further important issues were the reduction of fuel consumption per m3 harvested, increased use of fuelwood and non-wood forest products, as well as use of GIS and GPS in wood harvesting operations and forest engineering.	Важными вопросами являются сокращение потребления топлива в расчете на мЗ заготовленной древесины, расширение использования топливной древесины и недревесных лесных товаров, а также использование ГИС и ГСМ при проведении лесозаготовительных операций и в рамках лесоустройства.
In the past the possibility of using the GPS within the ZSR network was tested.	В прошлом была изучена возможность применения ГСМ на сети Словацких железных дорог.
Nationwide Differential GPS is an augmentation of the Global Positioning System that provides 1- to 3-meter positioning accuracy to receivers capable of receiving the differential correction signal.	Национальный дифференциал ГСМ является продолжением Глобальной системы местоопределения, которая выдает пользователям, способным принимать скорректированный дифференционный сигнал, информацию о местоположении с точностью 1-3 м.

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Глс (примеров 12)

Global positioning systems (GPS) were now starting to be used to track road transport.	В настоящее время для контроля за автомобильными перевозками начинают использоваться глобальные локализационные системы (ГЛС).
It is suggested that Global Positioning Systems (GPS) are necessary during data collection to accomplish this task and require a considerable investment by countries.	Предполагается, что для выполнения этой задачи необходимо в ходе сбора данных использовать Глобальные локализационные системы (ГЛС), требующие от стран значительных инвестиций.
The global positioning system (GPS) provides a precise and low-cost technology for land surveying and the establishment of a geographic information system (GIS).	Точной и недорогой технологией для геодезической съемки и создания географических информационных систем (ГИС) является глобальная локализационная система (ГЛС).
The military use of full Global Positioning System (GPS) capabilities, however, remain unavailable to civilian users.	Вместе с тем, гражданские пользователи по-прежнему не имеют возможности использовать в военных целях возможности Глобальной локационной системы (ГЛС) в целом.
(b) GPS is considered to be a cheap, accurate and fast method, in particular for the maintenance of cadastral maps and for establishing reference points for traditional surveying;	Ь) ГЛС считается недорогостоящим, точным и оперативным методом, в частности для ведения кадастровых карт и создания опорных точек для традиционной съемки;

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Джипиэс (примеров 9)

Spenser rented him a car, plugged the address into the GPS.	Спенсер нанял для него машину, вбил адрес в ДжиПиЭс.
Should I plug it into the GPS, or…?	Я должен подключить Джипиэс или…?
We’ve got GPS tracking on her mobile phone.	У неё на мобильном стоит ДжиПиЭс маяк.
Sir, if your phone’s GPS capability has been disabled, we’re going to have to triangulate your position through the cell towers to pinpoint your location.	Если на вашем телефоне отключена функция ДжиПиЭс, мы попытаемся засечь треугольник, в котором вы находитесь.
She will find Miles, but we will never find her, not without a GPS.	Она найдет Майлза, а вот мы никогда не найдем ее, во всяком случае без ДжиПиЭс точно.

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Гск (примеров 5)

Discrepancies between the earlier survey and ground evidence were settled with the use of GPS equipment.	Несоответствие данных ранее проведенного обследования фактическому положению на местности было устранено с помощью приборов ГСК.
Monitoring teams are also in the habit of verifying the range of missiles during in-flight testing, using helicopters to record the GPS coordinates of their points of launching and landing.	Кроме того, группы наблюдения, как правило, проверяют дальность, сообщаемую по итогам полетных испытаний, сопоставляя координаты (ГСК) точки запуска и точки падения, причем для этого используются вертолеты.
This would apply to initial visits to presidential sites and would not be regarded as a precedent for future visits since UNSCOM asserts its rights to use GPS instrumentation as standard equipment.	Этот компромисс будет распространяться только на первоначальные посещения президентских объектов и не будет рассматриваться в качестве прецедента для будущих посещений, поскольку ЮНСКОМ отстаивает свое право на использование приборов ГСК в качестве стандартного оборудования.
No difficulties were encountered with regard to aerial photography or the use of GPS instruments.	Никаких проблем с аэрофотосъемкой или использованием приборов ГСК не возникло.
(c) A list of GPS coordinates for each presidential site;	с) список координат ГСК по каждому президентскому объекту;

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Примеров нп (примеров 7)

Overall, 58 GPs were submitted by 21 countries and 2 intergovernmental organizations.	В общем и целом 21 страна и 2 межправительственные организации представили 58 примеров НП.
The full collection of GPs can be accessed online at: .	Полное собрание примеров НП доступно в Интернете по адресу: .
Identifying adequate funding for ESD remains challenging; yet several GPs achieved remarkable successes with very small budgets, suggesting that ingenuity, enthusiasm, and efficient use of limited resources can overcome financial pressures.	Проблемным остается поиск достаточного финансирования для ОУР, но, несмотря на это, в ряде примеров НП значительный успех был достигнут при очень небольшом бюджете, а это указывает на то, что с помощью находчивости и энтузиазма и при эффективном использовании ограниченных ресурсов можно преодолеть финансовые трудности.
While one of the main goals of the current collection of GPs was to identify how ESD can be used to promote sustainable consumption patterns, most of the examples provided by the countries identify the sustainability of ESD initiatives itself as a major challenge.	В то время как одной из основных целей данной подборки примеров НП было выяснение того, как ОУР может использоваться для поощрения устойчивых моделей потребления, в большинстве примеров, представленных странами, серьезной проблемой предстает обеспечение устойчивости самих инициатив ОУР.
This paper provides an analysis of trends and main lessons identified from the GPs.	В настоящем документе представлен анализ тенденций и основных извлеченных уроков на материале примеров НП.

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Джи пи эс (примеров 9)

~ Enter Grenoble on the GPS.	Вводи Гренобль в Джи Пи Эс.
The GPS readings, are they exact…	Данные Джи Пи Эс, насколько точны…
So with the help of some biologists studying the fungus, I got some maps and some GPS coordinates and chartered a plane and started looking for the death rings, the circular patterns in which the fungus kills the trees.	Итак, с помощью биологов, изучающих грибки, я получила карты, координаты Джи Пи Эс, заказала билет на самолёт и стала искать смертельные круги, округлые структуры, которыми грибок убивает деревья.
I have a GPS, okay?	Возьми мой Джи Пи Эс.
So with the help of some biologists studying the fungus, I got some maps and some GPS coordinates and chartered a plane and started looking for the death rings, the circular patterns in which the fungus kills the trees.	Итак, с помощью биологов, изучающих грибки, я получила карты, координаты Джи Пи Эс, заказала билет на самолёт и стала искать смертельные круги, округлые структуры, которыми грибок убивает деревья.

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Gps (примеров 404)

Its important for the GPS to be activated for the various functions in the GPS software to be activated and used properly.	Активация GPS необходима для нормальной работы различных функций навигационного программного обеспечения.
Both of these factors can distort GPS signals.	Их стены не пропускают также сигналы GPS.
Both watches run the Tizen operating system, have IP68 water resistance, GPS, and heart rate monitor sensors.	Оба модели часов работают под управлением операционной системы Tizen, имеют водостойкость, GPS и датчики контроля сердечного ритма.
Galileo info German with GPS threatens in 2010 the collapse?	Немецкий язык информации Galileo при GPS угрожает в 2010 коллапс?
The workshop was briefed on civil benefits of GPS modernization and noted that the setting of selective availability to zero was a first step in that process.	Участникам практикума было сообщено о гражданских выгодах, связанных с модернизацией GPS, и было отмечено, что первым шагом в этом процессе является отказ от режима выборочного доступа к услугам этой системы.

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Воп (примеров 9)

GPs remain the backbone of the health service, but the role of primary care is expanding.	ВОП остаются основой службы здравоохранения, но роль первичной медико-санитарной помощи возрастает.
Access to health care is detailed at Targets 28-30 of the Strategies Report — primary care (around 30,000 General Practitioners — GPs), hospital care (over 400 local hospitals), tertiary care and community services to meet special needs, respectively.	Подробная информация о доступе к медико-санитарной помощи содержится в показателях 2830 Доклада о стратегиях: первичная помощь (около 30000 врачей общей практики — ВОП), больничная помощь (свыше 400 местных больниц), высокоспециализированная помощь и специальные медицинские службы на местном уровне, соответственно.
Every year there are some 250 million GP consultations and some six million people visit a pharmacy every day. GPs remain the backbone of the health service, but the role of primary care is expanding.	Ежегодно ВОП принимает около 250 млн. пациентов, и каждый день около 6 млн. ВОП остаются основой службы здравоохранения, но роль первичной медико-санитарной помощи возрастает.
Contracts with GPs were held by County Public Health Directorates (CPHDs), terminating GPs‘ status as hospital employees.	Договоры с ВОП заключались уездными директоратами общественного здравоохранения (УДОЗ), что отменило статус ВОП как больничного персонала.
The system changed from the fixed allocation of patients to GPs according to residence to one with universal free choice of GP.	Эта система была изменена, и вместо жесткого закрепления пациентов за ВОП по месту жительства стала применяться система свободного выбора ВОП.

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Маячок (примеров 7)

All systems — cameras, phones, the GPS in your car can track us.	Все системы — камеры, телефоны, маячок в машине могут нас засечь.
Why did you cut your audio feed and your GPS?	Зачем ты отключил аудиотрансляцию и маячок?
The M.O.’s always the same… they hit right after a cash delivery, and they know how to find the GPS card.	Схема всегда одна: они нападают сразу после завоза налички, и они знаю, как найти маячок.
The teller dropped a GPS pack.	Кассирша подбросила маячок в сумку.
Then a warehouse manager found a GPS unit lying on the ground at a loading dock in Ladner.	А потом охранник склада нашел маячок на погрузочной площадке в Лэднере.

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This article is about the American global navigation satellite system. For similar systems, see Satellite navigation.

Global Positioning System (GPS)

Global Positioning System logo
Country/ies of origin	United States
Operator(s)	US Space Force
Type	Military, civilian
Status	Operational
Coverage	Global
Accuracy	30–500 cm (0.98–16 ft)
Constellation size
Total satellites	24
Satellites in orbit	32 (31 operational)
First launch	February 22, 1978; 45 years ago
Total launches	75
Orbital characteristics
Regime(s)	6 MEO planes
Orbital height	20,180 km (12,540 mi)
Other details
Cost	$12 billion[1] (initial constellation) $750 million per year[1] (operating cost)
Website	gps.gov

The Global Positioning System (GPS), originally Navstar GPS,^[2] is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force.^[3] It is one of the global navigation satellite systems (GNSS) that provides geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites.^[4] It does not require the user to transmit any data, and operates independently of any telephonic or Internet reception, though these technologies can enhance the usefulness of the GPS positioning information. It provides critical positioning capabilities to military, civil, and commercial users around the world. Although the United States government created, controls and maintains the GPS system, it is freely accessible to anyone with a GPS receiver.^[5]

The GPS project was started by the U.S. Department of Defense in 1973. The first prototype spacecraft was launched in 1978 and the full constellation of 24 satellites became operational in 1993. Originally limited to use by the United States military, civilian use was allowed from the 1980s following an executive order from President Ronald Reagan after the Korean Air Lines Flight 007 incident.^[6] Advances in technology and new demands on the existing system have now led to efforts to modernize the GPS and implement the next generation of GPS Block IIIA satellites and Next Generation Operational Control System (OCX).^[7] which was authorized by the U.S. Congress in 2000.

From the early 1990s, GPS positional accuracy was degraded by the United States government by a program called Selective Availability, which could selectively degrade or deny access to the system at any time,^[8] as happened to the Indian military in 1999 during the Kargil War. However, this practice was discontinued on May 1, 2000, in accordance with a bill signed into law by President Bill Clinton.^[9] As a result, several countries have developed or are in the process of setting up other global or regional satellite navigation systems.

The Russian Global Navigation Satellite System (GLONASS) was developed contemporaneously with GPS, but suffered from incomplete coverage of the globe until the mid-2000s.^[10] GLONASS reception in addition to GPS can be combined in a receiver thereby allowing for additional satellites available to enable faster position fixes and improved accuracy, to within two meters (6.6 ft).^[11][12]

China’s BeiDou Navigation Satellite System began global services in 2018, and finished its full deployment in 2020.^[13]
There are also the European Union Galileo navigation satellite system, and India’s NavIC. Japan’s Quasi-Zenith Satellite System (QZSS) is a GPS satellite-based augmentation system to enhance GPS’s accuracy in Asia-Oceania, with satellite navigation independent of GPS scheduled for 2023.^[14]

When selective availability was lifted in 2000, GPS had about a five-meter (16 ft) accuracy. GPS receivers that use the L5 band have much higher accuracy, pinpointing to within 30 centimeters (11.8 in), while high-end users (typically engineering and land surveying applications) are able to have accuracy on several of the bandwidth signals to within two centimeters, and even sub-millimeter accuracy for long-term measurements.^[9][15][16] Consumer devices, like smartphones, can be as accurate as to within 4.9 m (or better with assistive services like Wi-Fi positioning also enabled).^[17] As of May 2021, 16 GPS satellites are broadcasting L5 signals, and the signals are considered pre-operational, scheduled to reach 24 satellites by approximately 2027.

History[edit]

The GPS project was launched in the United States in 1973 to overcome the limitations of previous navigation systems,^[18] combining ideas from several predecessors, including classified engineering design studies from the 1960s. The U.S. Department of Defense developed the system, which originally used 24 satellites, for use by the United States military, and became fully operational in 1995. Civilian use was allowed from the 1980s. Roger L. Easton of the Naval Research Laboratory, Ivan A. Getting of The Aerospace Corporation, and Bradford Parkinson of the Applied Physics Laboratory are credited with inventing it.^[19] The work of Gladys West is credited as instrumental in the development of computational techniques for detecting satellite positions with the precision needed for GPS.^[20]

The design of GPS is based partly on similar ground-based radio-navigation systems, such as LORAN and the Decca Navigator, developed in the early 1940s.

In 1955, Friedwardt Winterberg proposed a test of general relativity—detecting time slowing in a strong gravitational field using accurate atomic clocks placed in orbit inside artificial satellites. Special and general relativity predicted that the clocks on GPS satellites, as observed by those on Earth, run 38 microseconds faster per day than those on the Earth. The design of GPS corrects for this difference; because without doing so, GPS calculated positions would accumulate errors of up to 10 kilometers per day (6 mi/d).^[21]

Predecessors[edit]

In 1955, Dutch Naval officer Wijnand Langeraar submitted a patent application for a radio-based Long-Range Navigation System, with the US Patent office on February 16, 1955, and was granted Patent US2980907A ^[22] on April 18, 1961.^{[original research?]}

When the Soviet Union launched the first artificial satellite (Sputnik 1) in 1957, two American physicists, William Guier and George Weiffenbach, at Johns Hopkins University’s Applied Physics Laboratory (APL) decided to monitor its radio transmissions.^[23] Within hours they realized that, because of the Doppler effect, they could pinpoint where the satellite was along its orbit. The Director of the APL gave them access to their UNIVAC to do the heavy calculations required.

Early the next year, Frank McClure, the deputy director of the APL, asked Guier and Weiffenbach to investigate the inverse problem: pinpointing the user’s location, given the satellite’s. (At the time, the Navy was developing the submarine-launched Polaris missile, which required them to know the submarine’s location.) This led them and APL to develop the TRANSIT system.^[24] In 1959, ARPA (renamed DARPA in 1972) also played a role in TRANSIT.^[25][26][27]

TRANSIT was first successfully tested in 1960.^[28] It used a constellation of five satellites and could provide a navigational fix approximately once per hour.

In 1967, the U.S. Navy developed the Timation satellite, which proved the feasibility of placing accurate clocks in space, a technology required for GPS.

In the 1970s, the ground-based OMEGA navigation system, based on phase comparison of signal transmission from pairs of stations,^[29] became the first worldwide radio navigation system. Limitations of these systems drove the need for a more universal navigation solution with greater accuracy.

Although there were wide needs for accurate navigation in military and civilian sectors, almost none of those was seen as justification for the billions of dollars it would cost in research, development, deployment, and operation of a constellation of navigation satellites. During the Cold War arms race, the nuclear threat to the existence of the United States was the one need that did justify this cost in the view of the United States Congress. This deterrent effect is why GPS was funded. It is also the reason for the ultra-secrecy at that time. The nuclear triad consisted of the United States Navy’s submarine-launched ballistic missiles (SLBMs) along with United States Air Force (USAF) strategic bombers and intercontinental ballistic missiles (ICBMs). Considered vital to the nuclear deterrence posture, accurate determination of the SLBM launch position was a force multiplier.

Precise navigation would enable United States ballistic missile submarines to get an accurate fix of their positions before they launched their SLBMs.^[30] The USAF, with two thirds of the nuclear triad, also had requirements for a more accurate and reliable navigation system. The U.S. Navy and U.S. Air Force were developing their own technologies in parallel to solve what was essentially the same problem.

To increase the survivability of ICBMs, there was a proposal to use mobile launch platforms (comparable to the Soviet SS-24 and SS-25) and so the need to fix the launch position had similarity to the SLBM situation.

In 1960, the Air Force proposed a radio-navigation system called MOSAIC (MObile System for Accurate ICBM Control) that was essentially a 3-D LORAN. A follow-on study, Project 57, was performed in 1963 and it was «in this study that the GPS concept was born.» That same year, the concept was pursued as Project 621B, which had «many of the attributes that you now see in GPS»^[31] and promised increased accuracy for Air Force bombers as well as ICBMs.

Updates from the Navy TRANSIT system were too slow for the high speeds of Air Force operation. The Naval Research Laboratory (NRL) continued making advances with their Timation (Time Navigation) satellites, first launched in 1967, second launched in 1969, with the third in 1974 carrying the first atomic clock into orbit and the fourth launched in 1977.^[32]

Another important predecessor to GPS came from a different branch of the United States military. In 1964, the United States Army orbited its first Sequential Collation of Range (SECOR) satellite used for geodetic surveying.^[33] The SECOR system included three ground-based transmitters at known locations that would send signals to the satellite transponder in orbit. A fourth ground-based station, at an undetermined position, could then use those signals to fix its location precisely. The last SECOR satellite was launched in 1969.^[34]

Development[edit]

With these parallel developments in the 1960s, it was realized that a superior system could be developed by synthesizing the best technologies from 621B, Transit, Timation, and SECOR in a multi-service program. Satellite orbital position errors, induced by variations in the gravity field and radar refraction among others, had to be resolved. A team led by Harold L Jury of Pan Am Aerospace Division in Florida from 1970 to 1973, used real-time data assimilation and recursive estimation to do so, reducing systematic and residual errors to a manageable level to permit accurate navigation.^[35]

During Labor Day weekend in 1973, a meeting of about twelve military officers at the Pentagon discussed the creation of a Defense Navigation Satellite System (DNSS). It was at this meeting that the real synthesis that became GPS was created. Later that year, the DNSS program was named Navstar.^[36] Navstar is often erroneously considered an acronym for «NAVigation System Using Timing and Ranging» but was never considered as such by the GPS Joint Program Office (TRW may have once advocated for a different navigational system that used that acronym).^[37] With the individual satellites being associated with the name Navstar (as with the predecessors Transit and Timation), a more fully encompassing name was used to identify the constellation of Navstar satellites, Navstar-GPS.^[38] Ten «Block I» prototype satellites were launched between 1978 and 1985 (an additional unit was destroyed in a launch failure).^[39]

The effect of the ionosphere on radio transmission was investigated in a geophysics laboratory of Air Force Cambridge Research Laboratory, renamed to Air Force Geophysical Research Lab (AFGRL) in 1974. AFGRL developed the Klobuchar model for computing ionospheric corrections to GPS location.^[40] Of note is work done by Australian space scientist Elizabeth Essex-Cohen at AFGRL in 1974. She was concerned with the curving of the paths of radio waves (atmospheric refraction) traversing the ionosphere from NavSTAR satellites.^[41]

After Korean Air Lines Flight 007, a Boeing 747 carrying 269 people, was shot down in 1983 after straying into the USSR’s prohibited airspace,^[42] in the vicinity of Sakhalin and Moneron Islands, President Ronald Reagan issued a directive making GPS freely available for civilian use, once it was sufficiently developed, as a common good.^[43] The first Block II satellite was launched on February 14, 1989,^[44] and the 24th satellite was launched in 1994. The GPS program cost at this point, not including the cost of the user equipment but including the costs of the satellite launches, has been estimated at US$5 billion (equivalent to $9 billion in 2021).^[45]

Initially, the highest-quality signal was reserved for military use, and the signal available for civilian use was intentionally degraded, in a policy known as Selective Availability. This changed with President Bill Clinton signing on May 1, 2000, a policy directive to turn off Selective Availability to provide the same accuracy to civilians that was afforded to the military. The directive was proposed by the U.S. Secretary of Defense, William Perry, in view of the widespread growth of differential GPS services by private industry to improve civilian accuracy. Moreover, the U.S. military was developing technologies to deny GPS service to potential adversaries on a regional basis.^[46] Selective Availability was removed from the GPS architecture beginning with GPS-III.

Since its deployment, the U.S. has implemented several improvements to the GPS service, including new signals for civil use and increased accuracy and integrity for all users, all the while maintaining compatibility with existing GPS equipment. Modernization of the satellite system has been an ongoing initiative by the U.S. Department of Defense through a series of satellite acquisitions to meet the growing needs of the military, civilians, and the commercial market.

As of early 2015, high-quality, FAA grade, Standard Positioning Service (SPS) GPS receivers provided horizontal accuracy of better than 3.5 meters (11 ft),^[47] although many factors such as receiver and antenna quality and atmospheric issues can affect this accuracy.

GPS is owned and operated by the United States government as a national resource. The Department of Defense is the steward of GPS. The Interagency GPS Executive Board (IGEB) oversaw GPS policy matters from 1996 to 2004. After that, the National Space-Based Positioning, Navigation and Timing Executive Committee was established by presidential directive in 2004 to advise and coordinate federal departments and agencies on matters concerning the GPS and related systems.^[48] The executive committee is chaired jointly by the Deputy Secretaries of Defense and Transportation. Its membership includes equivalent-level officials from the Departments of State, Commerce, and Homeland Security, the Joint Chiefs of Staff and NASA. Components of the executive office of the president participate as observers to the executive committee, and the FCC chairman participates as a liaison.

The U.S. Department of Defense is required by law to «maintain a Standard Positioning Service (as defined in the federal radio navigation plan and the standard positioning service signal specification) that will be available on a continuous, worldwide basis,» and «develop measures to prevent hostile use of GPS and its augmentations without unduly disrupting or degrading civilian uses.»

Timeline and modernization[edit]

Summary of satellites^[49][50][51]

Block	Launch period	Satellite launches	Currently in orbit and healthy
Suc- cess	Fail- ure	In prep- aration	Plan- ned
I	1978–1985	10	1	0	0	0
II	1989–1990	9	0	0	0	0
IIA	1990–1997	19	0	0	0	0
IIR	1997–2004	12	1	0	0	7
IIR-M	2005–2009	8	0	0	0	7
IIF	2010–2016	12	0	0	0	12
IIIA	2018–	5	0	5	0	5
IIIF	—	0	0	0	22	0
Total	75	2	5	22	31
(Last update: July 8, 2021) USA-203 from Block IIR-M is unhealthy [52] For a more complete list, see List of GPS satellites

• In 1972, the USAF Central Inertial Guidance Test Facility (Holloman AFB) conducted developmental flight tests of four prototype GPS receivers in a Y configuration over White Sands Missile Range, using ground-based pseudo-satellites.^[53]
• In 1978, the first experimental Block-I GPS satellite was launched.^[39]
• In 1983, after Soviet interceptor aircraft shot down the civilian airliner KAL 007 that strayed into prohibited airspace because of navigational errors, killing all 269 people on board, U.S. President Ronald Reagan announced that GPS would be made available for civilian uses once it was completed,^[54][55] although it had been previously published in Navigation magazine, and that the CA code (Coarse/Acquisition code) would be available to civilian users.^{[citation needed]}
• By 1985, ten more experimental Block-I satellites had been launched to validate the concept.
• Beginning in 1988, command and control of these satellites was moved from Onizuka AFS, California to the 2nd Satellite Control Squadron (2SCS) located at Falcon Air Force Station in Colorado Springs, Colorado.^[56][57]
• On February 14, 1989, the first modern Block-II satellite was launched.
• The Gulf War from 1990 to 1991 was the first conflict in which the military widely used GPS.^[58]
• In 1991, a project to create a miniature GPS receiver successfully ended, replacing the previous 16 kg (35 lb) military receivers with a 1.25 kg (2.8 lb) handheld receiver.^[26]
• In 1992, the 2nd Space Wing, which originally managed the system, was inactivated and replaced by the 50th Space Wing.

  

• By December 1993, GPS achieved initial operational capability (IOC), with a full constellation (24 satellites) available and providing the Standard Positioning Service (SPS).^[59]
• Full Operational Capability (FOC) was declared by Air Force Space Command (AFSPC) in April 1995, signifying full availability of the military’s secure Precise Positioning Service (PPS).^[59]
• In 1996, recognizing the importance of GPS to civilian users as well as military users, U.S. President Bill Clinton issued a policy directive^[60] declaring GPS a dual-use system and establishing an Interagency GPS Executive Board to manage it as a national asset.
• In 1998, United States Vice President Al Gore announced plans to upgrade GPS with two new civilian signals for enhanced user accuracy and reliability, particularly with respect to aviation safety, and in 2000 the United States Congress authorized the effort, referring to it as GPS III.
• On May 2, 2000 «Selective Availability» was discontinued as a result of the 1996 executive order, allowing civilian users to receive a non-degraded signal globally.
• In 2004, the United States government signed an agreement with the European Community establishing cooperation related to GPS and Europe’s Galileo system.
• In 2004, United States President George W. Bush updated the national policy and replaced the executive board with the National Executive Committee for Space-Based Positioning, Navigation, and Timing.^[61]
• November 2004, Qualcomm announced successful tests of assisted GPS for mobile phones.^[62]
• In 2005, the first modernized GPS satellite was launched and began transmitting a second civilian signal (L2C) for enhanced user performance.^[63]
• On September 14, 2007, the aging mainframe-based Ground Segment Control System was transferred to the new Architecture Evolution Plan.^[64]
• On May 19, 2009, the United States Government Accountability Office issued a report warning that some GPS satellites could fail as soon as 2010.^[65]
• On May 21, 2009, the Air Force Space Command allayed fears of GPS failure, saying «There’s only a small risk we will not continue to exceed our performance standard.»^[66]
• On January 11, 2010, an update of ground control systems caused a software incompatibility with 8,000 to 10,000 military receivers manufactured by a division of Trimble Navigation Limited of Sunnyvale, Calif.^{[citation needed][67]}
• On February 25, 2010,^[68] the U.S. Air Force awarded the contract^{[citation needed]} to develop the GPS Next Generation Operational Control System (OCX) to improve accuracy and availability of GPS navigation signals, and serve as a critical part of GPS modernization.

Awards[edit]

On February 10, 1993, the National Aeronautic Association selected the GPS Team as winners of the 1992 Robert J. Collier Trophy, the US’s most prestigious aviation award. This team combines researchers from the Naval Research Laboratory, the USAF, the Aerospace Corporation, Rockwell International Corporation, and IBM Federal Systems Company. The citation honors them «for the most significant development for safe and efficient navigation and surveillance of air and spacecraft since the introduction of radio navigation 50 years ago.»

Two GPS developers received the National Academy of Engineering Charles Stark Draper Prize for 2003:

• Ivan Getting, emeritus president of The Aerospace Corporation and an engineer at MIT, established the basis for GPS, improving on the World War II land-based radio system called LORAN (Long-range Radio Aid to Navigation).
• Bradford Parkinson, professor of aeronautics and astronautics at Stanford University, conceived the present satellite-based system in the early 1960s and developed it in conjunction with the U.S. Air Force. Parkinson served twenty-one years in the Air Force, from 1957 to 1978, and retired with the rank of colonel.

GPS developer Roger L. Easton received the National Medal of Technology on February 13, 2006.^[69]

Francis X. Kane (Col. USAF, ret.) was inducted into the U.S. Air Force Space and Missile Pioneers Hall of Fame at Lackland A.F.B., San Antonio, Texas, March 2, 2010, for his role in space technology development and the engineering design concept of GPS conducted as part of Project 621B.

In 1998, GPS technology was inducted into the Space Foundation Space Technology Hall of Fame.^[70]

On October 4, 2011, the International Astronautical Federation (IAF) awarded the Global Positioning System (GPS) its 60th Anniversary Award, nominated by IAF member, the American Institute for Aeronautics and Astronautics (AIAA). The IAF Honors and Awards Committee recognized the uniqueness of the GPS program and the exemplary role it has played in building international collaboration for the benefit of humanity.^[71]

On December 6, 2018, Gladys West was inducted into the Air Force Space and Missile Pioneers Hall of Fame in recognition of her work on an extremely accurate geodetic Earth model, which was ultimately used to determine the orbit of the GPS constellation.^[72]

On February 12, 2019, four founding members of the project were awarded the Queen Elizabeth Prize for Engineering with the chair of the awarding board stating «Engineering is the foundation of civilisation; there is no other foundation; it makes things happen. And that’s exactly what today’s Laureates have done — they’ve made things happen. They’ve re-written, in a major way, the infrastructure of our world.»^[73]

Principles[edit]

The GPS satellites carry very stable atomic clocks that are synchronized with one another and with the reference atomic clocks at the ground control stations; any drift of the clocks aboard the satellites from the reference time maintained on the ground stations is corrected regularly. Since the speed of radio waves (speed of light) is constant and independent of the satellite speed, the time delay between when the satellite transmits a signal and the ground station receives it is proportional to the distance from the satellite to the ground station. With the distance information collected from multiple ground stations, the location coordinates of any satellite at any time can be calculated with great precision.

Each GPS satellite carries an accurate record of its own position and time, and broadcasts that data continuously. Based on data received from multiple GPS satellites, an end user’s GPS receiver can calculate its own four-dimensional position in spacetime; However, at a minimum, four satellites must be in view of the receiver for it to compute four unknown quantities (three position coordinates and the deviation of its own clock from satellite time).

More detailed description[edit]

Each GPS satellite continually broadcasts a signal (carrier wave with modulation) that includes:

• A pseudorandom code (sequence of ones and zeros) that is known to the receiver. By time-aligning a receiver-generated version and the receiver-measured version of the code, the time of arrival (TOA) of a defined point in the code sequence, called an epoch, can be found in the receiver clock time scale
• A message that includes the time of transmission (TOT) of the code epoch (in GPS time scale) and the satellite position at that time

Conceptually, the receiver measures the TOAs (according to its own clock) of four satellite signals. From the TOAs and the TOTs, the receiver forms four time of flight (TOF) values, which are (given the speed of light) approximately equivalent to receiver-satellite ranges plus time difference between the receiver and GPS satellites multiplied by speed of light, which are called pseudo-ranges. The receiver then computes its three-dimensional position and clock deviation from the four TOFs.

In practice the receiver position (in three dimensional Cartesian coordinates with origin at the Earth’s center) and the offset of the receiver clock relative to the GPS time are computed simultaneously, using the navigation equations to process the TOFs.

The receiver’s Earth-centered solution location is usually converted to latitude, longitude and height relative to an ellipsoidal Earth model. The height may then be further converted to height relative to the geoid, which is essentially mean sea level. These coordinates may be displayed, such as on a moving map display, or recorded or used by some other system, such as a vehicle guidance system.

User-satellite geometry[edit]

Further information: § Geometric interpretation

Although usually not formed explicitly in the receiver processing, the conceptual time differences of arrival (TDOAs) define the measurement geometry. Each TDOA corresponds to a hyperboloid of revolution (see Multilateration). The line connecting the two satellites involved (and its extensions) forms the axis of the hyperboloid. The receiver is located at the point where three hyperboloids intersect.^[74][75]

It is sometimes incorrectly said that the user location is at the intersection of three spheres. While simpler to visualize, this is the case only if the receiver has a clock synchronized with the satellite clocks (i.e., the receiver measures true ranges to the satellites rather than range differences). There are marked performance benefits to the user carrying a clock synchronized with the satellites. Foremost is that only three satellites are needed to compute a position solution. If it were an essential part of the GPS concept that all users needed to carry a synchronized clock, a smaller number of satellites could be deployed, but the cost and complexity of the user equipment would increase.

Receiver in continuous operation[edit]

The description above is representative of a receiver start-up situation. Most receivers have a track algorithm, sometimes called a tracker, that combines sets of satellite measurements collected at different times—in effect, taking advantage of the fact that successive receiver positions are usually close to each other. After a set of measurements are processed, the tracker predicts the receiver location corresponding to the next set of satellite measurements. When the new measurements are collected, the receiver uses a weighting scheme to combine the new measurements with the tracker prediction. In general, a tracker can (a) improve receiver position and time accuracy, (b) reject bad measurements, and (c) estimate receiver speed and direction.

The disadvantage of a tracker is that changes in speed or direction can be computed only with a delay, and that derived direction becomes inaccurate when the distance traveled between two position measurements drops below or near the random error of position measurement. GPS units can use measurements of the Doppler shift of the signals received to compute velocity accurately.^[76] More advanced navigation systems use additional sensors like a compass or an inertial navigation system to complement GPS.

Non-navigation applications[edit]

For a list of applications, see § Applications.

GPS requires four or more satellites to be visible for accurate navigation. The solution of the navigation equations gives the position of the receiver along with the difference between the time kept by the receiver’s on-board clock and the true time-of-day, thereby eliminating the need for a more precise and possibly impractical receiver based clock. Applications for GPS such as time transfer, traffic signal timing, and synchronization of cell phone base stations, make use of this cheap and highly accurate timing. Some GPS applications use this time for display, or, other than for the basic position calculations, do not use it at all.

Although four satellites are required for normal operation, fewer apply in special cases. If one variable is already known, a receiver can determine its position using only three satellites. For example, a ship on the open ocean usually has a known elevation close to 0m, and the elevation of an aircraft may be known.^[a] Some GPS receivers may use additional clues or assumptions such as reusing the last known altitude, dead reckoning, inertial navigation, or including information from the vehicle computer, to give a (possibly degraded) position when fewer than four satellites are visible.^[77][78][79]

Structure[edit]

The current GPS consists of three major segments. These are the space segment, a control segment, and a user segment.^{[citation needed]} The U.S. Space Force develops, maintains, and operates the space and control segments. GPS satellites broadcast signals from space, and each GPS receiver uses these signals to calculate its three-dimensional location (latitude, longitude, and altitude) and the current time.^[80]

Space segment[edit]

The space segment (SS) is composed of 24 to 32 satellites, or Space Vehicles (SV), in medium Earth orbit, and also includes the payload adapters to the boosters required to launch them into orbit. The GPS design originally called for 24 SVs, eight each in three approximately circular orbits,^[81] but this was modified to six orbital planes with four satellites each.^[82] The six orbit planes have approximately 55° inclination (tilt relative to the Earth’s equator) and are separated by 60° right ascension of the ascending node (angle along the equator from a reference point to the orbit’s intersection).^[83] The orbital period is one-half a sidereal day, i.e., 11 hours and 58 minutes, so that the satellites pass over the same locations^[84] or almost the same locations^[85] every day. The orbits are arranged so that at least six satellites are always within line of sight from everywhere on the Earth’s surface (see animation at right).^[86] The result of this objective is that the four satellites are not evenly spaced (90°) apart within each orbit. In general terms, the angular difference between satellites in each orbit is 30°, 105°, 120°, and 105° apart, which sum to 360°.^[87]

Orbiting at an altitude of approximately 20,200 km (12,600 mi); orbital radius of approximately 26,600 km (16,500 mi),^[88] each SV makes two complete orbits each sidereal day, repeating the same ground track each day.^[89] This was very helpful during development because even with only four satellites, correct alignment means all four are visible from one spot for a few hours each day. For military operations, the ground track repeat can be used to ensure good coverage in combat zones.

As of February 2019,^[90] there are 31 satellites in the GPS constellation, 27 of which are in use at a given time with the rest allocated as stand-bys. A 32nd was launched in 2018, but as of July 2019 is still in evaluation. More decommissioned satellites are in orbit and available as spares. The additional satellites improve the precision of GPS receiver calculations by providing redundant measurements. With the increased number of satellites, the constellation was changed to a nonuniform arrangement. Such an arrangement was shown to improve accuracy but also improves reliability and availability of the system, relative to a uniform system, when multiple satellites fail.^[91] With the expanded constellation, nine satellites are usually visible at any time from any point on the Earth with a clear horizon, ensuring considerable redundancy over the minimum four satellites needed for a position.

Control segment[edit]

The control segment (CS) is composed of:

1. a master control station (MCS),
2. an alternative master control station,
3. four dedicated ground antennas, and
4. six dedicated monitor stations.

The MCS can also access Satellite Control Network (SCN) ground antennas (for additional command and control capability) and NGA (National Geospatial-Intelligence Agency) monitor stations. The flight paths of the satellites are tracked by dedicated U.S. Space Force monitoring stations in Hawaii, Kwajalein Atoll, Ascension Island, Diego Garcia, Colorado Springs, Colorado and Cape Canaveral, along with shared NGA monitor stations operated in England, Argentina, Ecuador, Bahrain, Australia and Washington DC.^[92] The tracking information is sent to the MCS at Schriever Space Force Base 25 km (16 mi) ESE of Colorado Springs, which is operated by the 2nd Space Operations Squadron (2 SOPS) of the U.S. Space Force. Then 2 SOPS contacts each GPS satellite regularly with a navigational update using dedicated or shared (AFSCN) ground antennas (GPS dedicated ground antennas are located at Kwajalein, Ascension Island, Diego Garcia, and Cape Canaveral). These updates synchronize the atomic clocks on board the satellites to within a few nanoseconds of each other, and adjust the ephemeris of each satellite’s internal orbital model. The updates are created by a Kalman filter that uses inputs from the ground monitoring stations, space weather information, and various other inputs.^[93]

Satellite maneuvers are not precise by GPS standards—so to change a satellite’s orbit, the satellite must be marked unhealthy, so receivers don’t use it. After the satellite maneuver, engineers track the new orbit from the ground, upload the new ephemeris, and mark the satellite healthy again.

The operation control segment (OCS) currently serves as the control segment of record. It provides the operational capability that supports GPS users and keeps the GPS operational and performing within specification.

OCS successfully replaced the legacy 1970s-era mainframe computer at Schriever Air Force Base in September 2007. After installation, the system helped enable upgrades and provide a foundation for a new security architecture that supported U.S. armed forces.

OCS will continue to be the ground control system of record until the new segment, Next Generation GPS Operation Control System^[7] (OCX), is fully developed and functional. The new capabilities provided by OCX will be the cornerstone for revolutionizing GPS’s mission capabilities, enabling^{[citation needed]} U.S. Space Force to greatly enhance GPS operational services to U.S. combat forces, civil partners and myriad domestic and international users. The GPS OCX program also will reduce cost, schedule and technical risk. It is designed to provide 50%^[94] sustainment cost savings through efficient software architecture and Performance-Based Logistics. In addition, GPS OCX is expected to cost millions less than the cost to upgrade OCS while providing four times the capability.

The GPS OCX program represents a critical part of GPS modernization and provides significant information assurance improvements over the current GPS OCS program.

• OCX will have the ability to control and manage GPS legacy satellites as well as the next generation of GPS III satellites, while enabling the full array of military signals.
• Built on a flexible architecture that can rapidly adapt to the changing needs of today’s and future GPS users allowing immediate access to GPS data and constellation status through secure, accurate and reliable information.
• Provides the warfighter with more secure, actionable and predictive information to enhance situational awareness.
• Enables new modernized signals (L1C, L2C, and L5) and has M-code capability, which the legacy system is unable to do.
• Provides significant information assurance improvements over the current program including detecting and preventing cyber attacks, while isolating, containing and operating during such attacks.
• Supports higher volume near real-time command and control capabilities and abilities.

On September 14, 2011,^[95] the U.S. Air Force announced the completion of GPS OCX Preliminary Design Review and confirmed that the OCX program is ready for the next phase of development.

The GPS OCX program has missed major milestones and pushed its launch into 2021, 5 years past the original deadline. According to the Government Accounting Office in 2019, the 2021 deadline looked shaky.^{[96][needs update]}

User segment[edit]

The user segment (US) is composed of hundreds of thousands of U.S. and allied military users of the secure GPS Precise Positioning Service, and tens of millions of civil, commercial and scientific users of the Standard Positioning Service. In general, GPS receivers are composed of an antenna, tuned to the frequencies transmitted by the satellites, receiver-processors, and a highly stable clock (often a crystal oscillator). They may also include a display for providing location and speed information to the user. A receiver is often described by its number of channels: this signifies how many satellites it can monitor simultaneously. Originally limited to four or five, this has progressively increased over the years so that, as of 2007, receivers typically have between 12 and 20 channels. Though there are many receiver manufacturers, they almost all use one of the chipsets produced for this purpose.^{[citation needed]}

GPS receivers may include an input for differential corrections, using the RTCM SC-104 format. This is typically in the form of an RS-232 port at 4,800 bit/s speed. Data is actually sent at a much lower rate, which limits the accuracy of the signal sent using RTCM.^{[citation needed]} Receivers with internal DGPS receivers can outperform those using external RTCM data.^{[citation needed]} As of 2006, even low-cost units commonly include Wide Area Augmentation System (WAAS) receivers.

Many GPS receivers can relay position data to a PC or other device using the NMEA 0183 protocol. Although this protocol is officially defined by the National Marine Electronics Association (NMEA),^[97] references to this protocol have been compiled from public records, allowing open source tools like gpsd to read the protocol without violating intellectual property laws.^{[clarification needed]} Other proprietary protocols exist as well, such as the SiRF and MTK protocols. Receivers can interface with other devices using methods including a serial connection, USB, or Bluetooth.

Applications[edit]

While originally a military project, GPS is considered a dual-use technology, meaning it has significant civilian applications as well.

GPS has become a widely deployed and useful tool for commerce, scientific uses, tracking, and surveillance. GPS’s accurate time facilitates everyday activities such as banking, mobile phone operations, and even the control of power grids by allowing well synchronized hand-off switching.^[80]

Civilian[edit]

Many civilian applications use one or more of GPS’s three basic components: absolute location, relative movement, and time transfer.

• Amateur radio: clock synchronization required for several digital modes such as FT8, FT4 and JS8; also used with APRS for position reporting; is often critical during emergency and disaster communications support.
• Atmosphere: studying the troposphere delays (recovery of the water vapor content) and ionosphere delays (recovery of the number of free electrons).^[98] Recovery of Earth surface displacements due to the atmospheric pressure loading.^[99]
• Astronomy: both positional and clock synchronization data is used in astrometry and celestial mechanics and precise orbit determination.^[100] GPS is also used in both amateur astronomy with small telescopes as well as by professional observatories for finding extrasolar planets.
• Automated vehicle: applying location and routes for cars and trucks to function without a human driver.
• Cartography: both civilian and military cartographers use GPS extensively.
• Cellular telephony: clock synchronization enables time transfer, which is critical for synchronizing its spreading codes with other base stations to facilitate inter-cell handoff and support hybrid GPS/cellular position detection for mobile emergency calls and other applications. The first handsets with integrated GPS launched in the late 1990s. The U.S. Federal Communications Commission (FCC) mandated the feature in either the handset or in the towers (for use in triangulation) in 2002 so emergency services could locate 911 callers. Third-party software developers later gained access to GPS APIs from Nextel upon launch, followed by Sprint in 2006, and Verizon soon thereafter.
• Clock synchronization: the accuracy of GPS time signals (±10 ns)^[101] is second only to the atomic clocks they are based on, and is used in applications such as GPS disciplined oscillators.
• Disaster relief/emergency services: many emergency services depend upon GPS for location and timing capabilities.
• GPS-equipped radiosondes and dropsondes: measure and calculate the atmospheric pressure, wind speed and direction up to 27 km (89,000 ft) from the Earth’s surface.
• Radio occultation for weather and atmospheric science applications.^[102]
• Fleet tracking: used to identify, locate and maintain contact reports with one or more fleet vehicles in real-time.
• Geodesy: determination of Earth orientation parameters including the daily and sub-daily polar motion,^[103] and length-of-day variabilities,^[104] Earth’s center-of-mass — geocenter motion,^[105] and low-degree gravity field parameters.^[106]
• Geofencing: vehicle tracking systems, person tracking systems, and pet tracking systems use GPS to locate devices that are attached to or carried by a person, vehicle, or pet. The application can provide continuous tracking and send notifications if the target leaves a designated (or «fenced-in») area.^[107]
• Geotagging: applies location coordinates to digital objects such as photographs (in Exif data) and other documents for purposes such as creating map overlays with devices like Nikon GP-1
• GPS aircraft tracking
• GPS for mining: the use of RTK GPS has significantly improved several mining operations such as drilling, shoveling, vehicle tracking, and surveying. RTK GPS provides centimeter-level positioning accuracy.
• GPS data mining: It is possible to aggregate GPS data from multiple users to understand movement patterns, common trajectories and interesting locations.^[108]
• GPS tours: location determines what content to display; for instance, information about an approaching point of interest.
• Mental health: tracking mental health functioning and sociability.^[109]
• Navigation: navigators value digitally precise velocity and orientation measurements, as well as precise positions in real-time with a support of orbit and clock corrections.^[110]
• Orbit determination of low-orbiting satellites with GPS receiver installed on board, such as GOCE,^[111] GRACE, Jason-1, Jason-2, TerraSAR-X, TanDEM-X, CHAMP, Sentinel-3,^[112] and some cubesats, e.g., CubETH.
• Phasor measurements: GPS enables highly accurate timestamping of power system measurements, making it possible to compute phasors.
• Recreation: for example, Geocaching, Geodashing, GPS drawing, waymarking, and other kinds of location based mobile games such as Pokémon Go.
• Reference frames: realization and densification of the terrestrial reference frames^[113] in the framework of Global Geodetic Observing System. Co-location in space between Satellite laser ranging^[114] and microwave observations^[115] for deriving global geodetic parameters.^[116][117]
• Robotics: self-navigating, autonomous robots using GPS sensors,^[118] which calculate latitude, longitude, time, speed, and heading.
• Sport: used in football and rugby for the control and analysis of the training load.^[119]
• Surveying: surveyors use absolute locations to make maps and determine property boundaries.
• Tectonics: GPS enables direct fault motion measurement of earthquakes. Between earthquakes GPS can be used to measure crustal motion and deformation^[120] to estimate seismic strain buildup for creating seismic hazard maps.
• Telematics: GPS technology integrated with computers and mobile communications technology in automotive navigation systems.

Restrictions on civilian use[edit]

The U.S. government controls the export of some civilian receivers. All GPS receivers capable of functioning above 60,000 ft (18 km) above sea level and 1,000 kn (500 m/s; 2,000 km/h; 1,000 mph), or designed or modified for use with unmanned missiles and aircraft, are classified as munitions (weapons)—which means they require State Department export licenses.^[121] This rule applies even to otherwise purely civilian units that only receive the L1 frequency and the C/A (Coarse/Acquisition) code.

Disabling operation above these limits exempts the receiver from classification as a munition. Vendor interpretations differ. The rule refers to operation at both the target altitude and speed, but some receivers stop operating even when stationary. This has caused problems with some amateur radio balloon launches that regularly reach 30 km (100,000 feet).

These limits only apply to units or components exported from the United States. A growing trade in various components exists, including GPS units from other countries. These are expressly sold as ITAR-free.

Military[edit]

As of 2009, military GPS applications include:

• Navigation: Soldiers use GPS to find objectives, even in the dark or in unfamiliar territory, and to coordinate troop and supply movement. In the United States armed forces, commanders use the Commander’s Digital Assistant and lower ranks use the Soldier Digital Assistant.^[122]
• Target tracking: Various military weapons systems use GPS to track potential ground and air targets before flagging them as hostile.^{[citation needed]} These weapon systems pass target coordinates to precision-guided munitions to allow them to engage targets accurately. Military aircraft, particularly in air-to-ground roles, use GPS to find targets.
• Missile and projectile guidance: GPS allows accurate targeting of various military weapons including ICBMs, cruise missiles, precision-guided munitions and artillery shells. Embedded GPS receivers able to withstand accelerations of 12,000 g or about 118 km/s² (260,000 mph/s) have been developed for use in 155-millimeter (6.1 in) howitzer shells.^{[citation needed]}
• Search and rescue.
• Reconnaissance: Patrol movement can be managed more closely.
• GPS satellites carry a set of nuclear detonation detectors consisting of an optical sensor called a bhangmeter, an X-ray sensor, a dosimeter, and an electromagnetic pulse (EMP) sensor (W-sensor), that form a major portion of the United States Nuclear Detonation Detection System.^[123][124] General William Shelton has stated that future satellites may drop this feature to save money.^[125]

GPS type navigation was first used in war in the 1991 Persian Gulf War, before GPS was fully developed in 1995, to assist Coalition Forces to navigate and perform maneuvers in the war. The war also demonstrated the vulnerability of GPS to being jammed, when Iraqi forces installed jamming devices on likely targets that emitted radio noise, disrupting reception of the weak GPS signal.^[126]

GPS’s vulnerability to jamming is a threat that continues to grow as jamming equipment and experience grows.^[127][128] GPS signals have been reported to have been jammed many times over the years for military purposes. Russia seems to have several objectives for this behavior, such as intimidating neighbors while undermining confidence in their reliance on American systems, promoting their GLONASS alternative, disrupting Western military exercises, and protecting assets from drones.^[129] China uses jamming to discourage US surveillance aircraft near the contested Spratly Islands.^[130] North Korea has mounted several major jamming operations near its border with South Korea and offshore, disrupting flights, shipping and fishing operations.^[131] Iranian Armed Forces disrupted the civilian airliner plane Flight PS752’s GPS when it shot down the aircraft.^[132][133]

Timekeeping [edit]

Leap seconds[edit]

While most clocks derive their time from Coordinated Universal Time (UTC), the atomic clocks on the satellites are set to GPS time. The difference is that GPS time is not corrected to match the rotation of the Earth, so it does not contain new leap seconds or other corrections that are periodically added to UTC. GPS time was set to match UTC in 1980, but has since diverged. The lack of corrections means that GPS time remains at a constant offset with International Atomic Time (TAI) (TAI — GPS = 19 seconds). Periodic corrections are performed to the on-board clocks to keep them synchronized with ground clocks.^[134]

The GPS navigation message includes the difference between GPS time and UTC. As of January 2017, GPS time is 18 seconds ahead of UTC because of the leap second added to UTC on December 31, 2016.^[135] Receivers subtract this offset from GPS time to calculate UTC and specific time zone values. New GPS units may not show the correct UTC time until after receiving the UTC offset message. The GPS-UTC offset field can accommodate 255 leap seconds (eight bits).

Accuracy[edit]

GPS time is theoretically accurate to about 14 nanoseconds, due to the clock drift relative to International Atomic Time that the atomic clocks in GPS transmitters experience^[136] Most receivers lose some accuracy in their interpretation of the signals and are only accurate to about 100 nanoseconds.^[137][138]

Relativistic corrections[edit]

The GPS implements two major corrections to its time signals for relativistic effects: one for relative velocity of satellite and receiver, using the special theory of relativity, and one for the difference in gravitational potential between satellite and receiver, using general relativity. The acceleration of the satellite could also be computed independently as a correction, depending on purpose, but normally the effect is already dealt with in the first two corrections.^[139][140]

Format[edit]

As opposed to the year, month, and day format of the Gregorian calendar, the GPS date is expressed as a week number and a seconds-into-week number. The week number is transmitted as a ten-bit field in the C/A and P(Y) navigation messages, and so it becomes zero again every 1,024 weeks (19.6 years). GPS week zero started at 00:00:00 UTC (00:00:19 TAI) on January 6, 1980, and the week number became zero again for the first time at 23:59:47 UTC on August 21, 1999 (00:00:19 TAI on August 22, 1999). It happened the second time at 23:59:42 UTC on April 6, 2019. To determine the current Gregorian date, a GPS receiver must be provided with the approximate date (to within 3,584 days) to correctly translate the GPS date signal. To address this concern in the future the modernized GPS civil navigation (CNAV) message will use a 13-bit field that only repeats every 8,192 weeks (157 years), thus lasting until 2137 (157 years after GPS week zero).

Communication[edit]

The navigational signals transmitted by GPS satellites encode a variety of information including satellite positions, the state of the internal clocks, and the health of the network. These signals are transmitted on two separate carrier frequencies that are common to all satellites in the network. Two different encodings are used: a public encoding that enables lower resolution navigation, and an encrypted encoding used by the U.S. military.

Message format[edit]

GPS message format

Subframes	Description
1	Satellite clock, GPS time relationship
2–3	Ephemeris (precise satellite orbit)
4–5	Almanac component (satellite network synopsis, error correction)

Each GPS satellite continuously broadcasts a navigation message on L1 (C/A and P/Y) and L2 (P/Y) frequencies at a rate of 50 bits per second (see bitrate). Each complete message takes 750 seconds (12+1⁄2 minutes) to complete. The message structure has a basic format of a 1500-bit-long frame made up of five subframes, each subframe being 300 bits (6 seconds) long. Subframes 4 and 5 are subcommutated 25 times each, so that a complete data message requires the transmission of 25 full frames. Each subframe consists of ten words, each 30 bits long. Thus, with 300 bits in a subframe times 5 subframes in a frame times 25 frames in a message, each message is 37,500 bits long. At a transmission rate of 50-bit/s, this gives 750 seconds to transmit an entire almanac message (GPS). Each 30-second frame begins precisely on the minute or half-minute as indicated by the atomic clock on each satellite.^[141]

The first subframe of each frame encodes the week number and the time within the week,^[142] as well as the data about the health of the satellite. The second and the third subframes contain the ephemeris – the precise orbit for the satellite. The fourth and fifth subframes contain the almanac, which contains coarse orbit and status information for up to 32 satellites in the constellation as well as data related to error correction. Thus, to obtain an accurate satellite location from this transmitted message, the receiver must demodulate the message from each satellite it includes in its solution for 18 to 30 seconds. To collect all transmitted almanacs, the receiver must demodulate the message for 732 to 750 seconds or 12+1⁄2 minutes.^[143]

All satellites broadcast at the same frequencies, encoding signals using unique code-division multiple access (CDMA) so receivers can distinguish individual satellites from each other. The system uses two distinct CDMA encoding types: the coarse/acquisition (C/A) code, which is accessible by the general public, and the precise (P(Y)) code, which is encrypted so that only the U.S. military and other NATO nations who have been given access to the encryption code can access it.^[144]

The ephemeris is updated every 2 hours and is sufficiently stable for 4 hours, with provisions for updates every 6 hours or longer in non-nominal conditions. The almanac is updated typically every 24 hours. Additionally, data for a few weeks following is uploaded in case of transmission updates that delay data upload.^{[citation needed]}

Satellite frequencies[edit]

GPS frequency overview^[145]: 607

Band	Frequency	Description
L1	1575.42 MHz	Coarse-acquisition (C/A) and encrypted precision (P(Y)) codes, plus the L1 civilian (L1C) and military (M) codes on Block III and newer satellites.
L2	1227.60 MHz	P(Y) code, plus the L2C and military codes on the Block IIR-M and newer satellites.
L3	1381.05 MHz	Used for nuclear detonation (NUDET) detection.
L4	1379.913 MHz	Being studied for additional ionospheric correction.
L5	1176.45 MHz	Used as a civilian safety-of-life (SoL) signal on Block IIF and newer satellites.

All satellites broadcast at the same two frequencies, 1.57542 GHz (L1 signal) and 1.2276 GHz (L2 signal). The satellite network uses a CDMA spread-spectrum technique^[145]: 607 where the low-bitrate message data is encoded with a high-rate pseudo-random (PRN) sequence that is different for each satellite. The receiver must be aware of the PRN codes for each satellite to reconstruct the actual message data. The C/A code, for civilian use, transmits data at 1.023 million chips per second, whereas the P code, for U.S. military use, transmits at 10.23 million chips per second. The actual internal reference of the satellites is 10.22999999543 MHz to compensate for relativistic effects^[146][147] that make observers on the Earth perceive a different time reference with respect to the transmitters in orbit. The L1 carrier is modulated by both the C/A and P codes, while the L2 carrier is only modulated by the P code.^[87] The P code can be encrypted as a so-called P(Y) code that is only available to military equipment with a proper decryption key. Both the C/A and P(Y) codes impart the precise time-of-day to the user.

The L3 signal at a frequency of 1.38105 GHz is used to transmit data from the satellites to ground stations. This data is used by the United States Nuclear Detonation (NUDET) Detection System (USNDS) to detect, locate, and report nuclear detonations (NUDETs) in the Earth’s atmosphere and near space.^[148] One usage is the enforcement of nuclear test ban treaties.

The L4 band at 1.379913 GHz is being studied for additional ionospheric correction.^[145]: 607

The L5 frequency band at 1.17645 GHz was added in the process of GPS modernization. This frequency falls into an internationally protected range for aeronautical navigation, promising little or no interference under all circumstances. The first Block IIF satellite that provides this signal was launched in May 2010.^[149] On February 5, 2016, the 12th and final Block IIF satellite was launched.^[150] The L5 consists of two carrier components that are in phase quadrature with each other. Each carrier component is bi-phase shift key (BPSK) modulated by a separate bit train. «L5, the third civil GPS signal, will eventually support safety-of-life applications for aviation and provide improved availability and accuracy.»^[151]

This section needs to be updated. Please help update this article to reflect recent events or newly available information. (May 2021)

In 2011, a conditional waiver was granted to LightSquared to operate a terrestrial broadband service near the L1 band. Although LightSquared had applied for a license to operate in the 1525 to 1559 band as early as 2003 and it was put out for public comment, the FCC asked LightSquared to form a study group with the GPS community to test GPS receivers and identify issue that might arise due to the larger signal power from the LightSquared terrestrial network. The GPS community had not objected to the LightSquared (formerly MSV and SkyTerra) applications until November 2010, when LightSquared applied for a modification to its Ancillary Terrestrial Component (ATC) authorization. This filing (SAT-MOD-20101118-00239) amounted to a request to run several orders of magnitude more power in the same frequency band for terrestrial base stations, essentially repurposing what was supposed to be a «quiet neighborhood» for signals from space as the equivalent of a cellular network. Testing in the first half of 2011 has demonstrated that the impact of the lower 10 MHz of spectrum is minimal to GPS devices (less than 1% of the total GPS devices are affected). The upper 10 MHz intended for use by LightSquared may have some impact on GPS devices. There is some concern that this may seriously degrade the GPS signal for many consumer uses.^[152][153] Aviation Week magazine reports that the latest testing (June 2011) confirms «significant jamming» of GPS by LightSquared’s system.^[154]

Demodulation and decoding[edit]

Because all of the satellite signals are modulated onto the same L1 carrier frequency, the signals must be separated after demodulation. This is done by assigning each satellite a unique binary sequence known as a Gold code. The signals are decoded after demodulation using addition of the Gold codes corresponding to the satellites monitored by the receiver.^[155][156]

If the almanac information has previously been acquired, the receiver picks the satellites to listen for by their PRNs, unique numbers in the range 1 through 32. If the almanac information is not in memory, the receiver enters a search mode until a lock is obtained on one of the satellites. To obtain a lock, it is necessary that there be an unobstructed line of sight from the receiver to the satellite. The receiver can then acquire the almanac and determine the satellites it should listen for. As it detects each satellite’s signal, it identifies it by its distinct C/A code pattern. There can be a delay of up to 30 seconds before the first estimate of position because of the need to read the ephemeris data.

Processing of the navigation message enables the determination of the time of transmission and the satellite position at this time. For more information see Demodulation and Decoding, Advanced.

Navigation equations[edit]

Problem statement[edit]

The receiver uses messages received from satellites to determine the satellite positions and time sent. The x, y, and z components of satellite position and the time sent (s) are designated as [x_i, y_i, z_i, s_i] where the subscript i denotes the satellite and has the value 1, 2, …, n, where n ≥ 4. When the time of message reception indicated by the on-board receiver clock is , the true reception time is , where b is the receiver’s clock bias from the much more accurate GPS clocks employed by the satellites. The receiver clock bias is the same for all received satellite signals (assuming the satellite clocks are all perfectly synchronized). The message’s transit time is , where s_i is the satellite time. Assuming the message traveled at the speed of light, c, the distance traveled is .

For n satellites, the equations to satisfy are:

where d_i is the geometric distance or range between receiver and satellite i (the values without subscripts are the x, y, and z components of receiver position):

Defining pseudoranges as , we see they are biased versions of the true range:

.^[157][158]

Since the equations have four unknowns [x, y, z, b]—the three components of GPS receiver position and the clock bias—signals from at least four satellites are necessary to attempt solving these equations. They can be solved by algebraic or numerical methods. Existence and uniqueness of GPS solutions are discussed by Abell and Chaffee.^[74] When n is greater than four, this system is overdetermined and a fitting method must be used.

The amount of error in the results varies with the received satellites’ locations in the sky, since certain configurations (when the received satellites are close together in the sky) cause larger errors. Receivers usually calculate a running estimate of the error in the calculated position. This is done by multiplying the basic resolution of the receiver by quantities called the geometric dilution of position (GDOP) factors, calculated from the relative sky directions of the satellites used.^[159] The receiver location is expressed in a specific coordinate system, such as latitude and longitude using the WGS 84 geodetic datum or a country-specific system.^[160]

Geometric interpretation[edit]

The GPS equations can be solved by numerical and analytical methods. Geometrical interpretations can enhance the understanding of these solution methods.

Spheres[edit]

The measured ranges, called pseudoranges, contain clock errors. In a simplified idealization in which the ranges are synchronized, these true ranges represent the radii of spheres, each centered on one of the transmitting satellites. The solution for the position of the receiver is then at the intersection of the surfaces of these spheres; see trilateration (more generally, true-range multilateration). Signals from at minimum three satellites are required, and their three spheres would typically intersect at two points.^[161] One of the points is the location of the receiver, and the other moves rapidly in successive measurements and would not usually be on Earth’s surface.

In practice, there are many sources of inaccuracy besides clock bias, including random errors as well as the potential for precision loss from subtracting numbers close to each other if the centers of the spheres are relatively close together. This means that the position calculated from three satellites alone is unlikely to be accurate enough. Data from more satellites can help because of the tendency for random errors to cancel out and also by giving a larger spread between the sphere centers. But at the same time, more spheres will not generally intersect at one point. Therefore, a near intersection gets computed, typically via least squares. The more signals available, the better the approximation is likely to be.

Hyperboloids[edit]

If the pseudorange between the receiver and satellite i and the pseudorange between the receiver and satellite j are subtracted, p_i − p_j, the common receiver clock bias (b) cancels out, resulting in a difference of distances d_i − d_j. The locus of points having a constant difference in distance to two points (here, two satellites) is a hyperbola on a plane and a hyperboloid of revolution (more specifically, a two-sheeted hyperboloid) in 3D space (see Multilateration). Thus, from four pseudorange measurements, the receiver can be placed at the intersection of the surfaces of three hyperboloids each with foci at a pair of satellites. With additional satellites, the multiple intersections are not necessarily unique, and a best-fitting solution is sought instead.^{[74][75][162][163][164][165]}

Inscribed sphere[edit]

The receiver position can be interpreted as the center of an inscribed sphere (insphere) of radius bc, given by the receiver clock bias b (scaled by the speed of light c). The insphere location is such that it touches other spheres. The circumscribing spheres are centered at the GPS satellites, whose radii equal the measured pseudoranges p_i. This configuration is distinct from the one described above, in which the spheres’ radii were the unbiased or geometric ranges d_i.^{[164]: 36–37 [166]}

Hypercones[edit]

The clock in the receiver is usually not of the same quality as the ones in the satellites and will not be accurately synchronized to them. This produces pseudoranges with large differences compared to the true distances to the satellites. Therefore, in practice, the time difference between the receiver clock and the satellite time is defined as an unknown clock bias b. The equations are then solved simultaneously for the receiver position and the clock bias. The solution space [x, y, z, b] can be seen as a four-dimensional spacetime, and signals from at minimum four satellites are needed. In that case each of the equations describes a hypercone (or spherical cone),^[167] with the cusp located at the satellite, and the base a sphere around the satellite. The receiver is at the intersection of four or more of such hypercones.

Solution methods[edit]

Least squares[edit]

When more than four satellites are available, the calculation can use the four best, or more than four simultaneously (up to all visible satellites), depending on the number of receiver channels, processing capability, and geometric dilution of precision (GDOP).

Using more than four involves an over-determined system of equations with no unique solution; such a system can be solved by a least-squares or weighted least squares method.^[157]

Iterative[edit]

Both the equations for four satellites, or the least squares equations for more than four, are non-linear and need special solution methods. A common approach is by iteration on a linearized form of the equations, such as the Gauss–Newton algorithm.

The GPS was initially developed assuming use of a numerical least-squares solution method—i.e., before closed-form solutions were found.

Closed-form[edit]

One closed-form solution to the above set of equations was developed by S. Bancroft.^[158][168] Its properties are well known;^{[74][75][169]} in particular, proponents claim it is superior in low-GDOP situations, compared to iterative least squares methods.^[168]

Bancroft’s method is algebraic, as opposed to numerical, and can be used for four or more satellites. When four satellites are used, the key steps are inversion of a 4×4 matrix and solution of a single-variable quadratic equation. Bancroft’s method provides one or two solutions for the unknown quantities. When there are two (usually the case), only one is a near-Earth sensible solution.^[158]

When a receiver uses more than four satellites for a solution, Bancroft uses the generalized inverse (i.e., the pseudoinverse) to find a solution. A case has been made that iterative methods, such as the Gauss–Newton algorithm approach for solving over-determined non-linear least squares problems, generally provide more accurate solutions.^[170]

Leick et al. (2015) states that «Bancroft’s (1985) solution is a very early, if not the first, closed-form solution.»^[171]
Other closed-form solutions were published afterwards,^[172][173] although their adoption in practice is unclear.

Error sources and analysis[edit]

GPS error analysis examines error sources in GPS results and the expected size of those errors. GPS makes corrections for receiver clock errors and other effects, but some residual errors remain uncorrected. Error sources include signal arrival time measurements, numerical calculations, atmospheric effects (ionospheric/tropospheric delays), ephemeris and clock data, multipath signals, and natural and artificial interference. Magnitude of residual errors from these sources depends on geometric dilution of precision. Artificial errors may result from jamming devices and threaten ships and aircraft^[174] or from intentional signal degradation through selective availability, which limited accuracy to ≈ 6–12 m (20–40 ft), but has been switched off since May 1, 2000.^[175][176]

Accuracy enhancement and surveying[edit]

Regulatory spectrum issues concerning GPS receivers[edit]

In the United States, GPS receivers are regulated under the Federal Communications Commission’s (FCC) Part 15 rules. As indicated in the manuals of GPS-enabled devices sold in the United States, as a Part 15 device, it «must accept any interference received, including interference that may cause undesired operation.»^[177] With respect to GPS devices in particular, the FCC states that GPS receiver manufacturers, «must use receivers that reasonably discriminate against reception of signals outside their allocated spectrum.»^[178] For the last 30 years, GPS receivers have operated next to the Mobile Satellite Service band, and have discriminated against reception of mobile satellite services, such as Inmarsat, without any issue.

The spectrum allocated for GPS L1 use by the FCC is 1559 to 1610 MHz, while the spectrum allocated for satellite-to-ground use owned by Lightsquared is the Mobile Satellite Service band.^[179] Since 1996, the FCC has authorized licensed use of the spectrum neighboring the GPS band of 1525 to 1559 MHz to the Virginia company LightSquared. On March 1, 2001, the FCC received an application from LightSquared’s predecessor, Motient Services, to use their allocated frequencies for an integrated satellite-terrestrial service.^[180] In 2002, the U.S. GPS Industry Council came to an out-of-band-emissions (OOBE) agreement with LightSquared to prevent transmissions from LightSquared’s ground-based stations from emitting transmissions into the neighboring GPS band of 1559 to 1610 MHz.^[181] In 2004, the FCC adopted the OOBE agreement in its authorization for LightSquared to deploy a ground-based network ancillary to their satellite system – known as the Ancillary Tower Components (ATCs) – «We will authorize MSS ATC subject to conditions that ensure that the added terrestrial component remains ancillary to the principal MSS offering. We do not intend, nor will we permit, the terrestrial component to become a stand-alone service.»^[182] This authorization was reviewed and approved by the U.S. Interdepartment Radio Advisory Committee, which includes the U.S. Department of Agriculture, U.S. Space Force, U.S. Army, U.S. Coast Guard, Federal Aviation Administration, National Aeronautics and Space Administration (NASA), U.S. Department of the Interior, and U.S. Department of Transportation.^[183]

In January 2011, the FCC conditionally authorized LightSquared’s wholesale customers—such as Best Buy, Sharp, and C Spire—to only purchase an integrated satellite-ground-based service from LightSquared and re-sell that integrated service on devices that are equipped to only use the ground-based signal using LightSquared’s allocated frequencies of 1525 to 1559 MHz.^[184] In December 2010, GPS receiver manufacturers expressed concerns to the FCC that LightSquared’s signal would interfere with GPS receiver devices^[185] although the FCC’s policy considerations leading up to the January 2011 order did not pertain to any proposed changes to the maximum number of ground-based LightSquared stations or the maximum power at which these stations could operate. The January 2011 order makes final authorization contingent upon studies of GPS interference issues carried out by a LightSquared led working group along with GPS industry and Federal agency participation. On February 14, 2012, the FCC initiated proceedings to vacate LightSquared’s Conditional Waiver Order based on the NTIA’s conclusion that there was currently no practical way to mitigate potential GPS interference.

GPS receiver manufacturers design GPS receivers to use spectrum beyond the GPS-allocated band. In some cases, GPS receivers are designed to use up to 400 MHz of spectrum in either direction of the L1 frequency of 1575.42 MHz, because mobile satellite services in those regions are broadcasting from space to ground, and at power levels commensurate with mobile satellite services.^[186] As regulated under the FCC’s Part 15 rules, GPS receivers are not warranted protection from signals outside GPS-allocated spectrum.^[178] This is why GPS operates next to the Mobile Satellite Service band, and also why the Mobile Satellite Service band operates next to GPS. The symbiotic relationship of spectrum allocation ensures that users of both bands are able to operate cooperatively and freely.

The FCC adopted rules in February 2003 that allowed Mobile Satellite Service (MSS) licensees such as LightSquared to construct a small number of ancillary ground-based towers in their licensed spectrum to «promote more efficient use of terrestrial wireless spectrum.»^[187] In those 2003 rules, the FCC stated «As a preliminary matter, terrestrial [Commercial Mobile Radio Service («CMRS»)] and MSS ATC are expected to have different prices, coverage, product acceptance and distribution; therefore, the two services appear, at best, to be imperfect substitutes for one another that would be operating in predominantly different market segments… MSS ATC is unlikely to compete directly with terrestrial CMRS for the same customer base…». In 2004, the FCC clarified that the ground-based towers would be ancillary, noting that «We will authorize MSS ATC subject to conditions that ensure that the added terrestrial component remains ancillary to the principal MSS offering. We do not intend, nor will we permit, the terrestrial component to become a stand-alone service.»^[182] In July 2010, the FCC stated that it expected LightSquared to use its authority to offer an integrated satellite-terrestrial service to «provide mobile broadband services similar to those provided by terrestrial mobile providers and enhance competition in the mobile broadband sector.»^[188] GPS receiver manufacturers have argued that LightSquared’s licensed spectrum of 1525 to 1559 MHz was never envisioned as being used for high-speed wireless broadband based on the 2003 and 2004 FCC ATC rulings making clear that the Ancillary Tower Component (ATC) would be, in fact, ancillary to the primary satellite component.^[189] To build public support of efforts to continue the 2004 FCC authorization of LightSquared’s ancillary terrestrial component vs. a simple ground-based LTE service in the Mobile Satellite Service band, GPS receiver manufacturer Trimble Navigation Ltd. formed the «Coalition To Save Our GPS.»^[190]

The FCC and LightSquared have each made public commitments to solve the GPS interference issue before the network is allowed to operate.^[191][192] According to Chris Dancy of the Aircraft Owners and Pilots Association, airline pilots with the type of systems that would be affected «may go off course and not even realize it.»^[193] The problems could also affect the Federal Aviation Administration upgrade to the air traffic control system, United States Defense Department guidance, and local emergency services including 911.^[193]

On February 14, 2012, the FCC moved to bar LightSquared’s planned national broadband network after being informed by the National Telecommunications and Information Administration (NTIA), the federal agency that coordinates spectrum uses for the military and other federal government entities, that «there is no practical way to mitigate potential interference at this time».^[194][195] LightSquared is challenging the FCC’s action.^{[needs update]}

Similar systems[edit]

Other notable satellite navigation systems in use or various states of development include:

• Beidou – system deployed and operated by the People’s Republic of China’s, initiating global services in 2019.^[196][197]
• Galileo – a global system being developed by the European Union and other partner countries, which began operation in 2016,^[198] and is expected to be fully deployed by 2020.^{[needs update]}
• GLONASS – Russia’s global navigation system. Fully operational worldwide.
• NavIC – a regional navigation system developed by the Indian Space Research Organisation.
• QZSS – a regional navigation system receivable in the Asia-Oceania regions, with a focus on Japan.

See also[edit]

Notes[edit]

References[edit]

Further reading[edit]

• «NAVSTAR GPS User Equipment Introduction» (PDF). United States Coast Guard. September 1996.
• Parkinson; Spilker (1996). The global positioning system. American Institute of Aeronautics and Astronautics. ISBN 978-1-56347-106-3.
• Jaizki Mendizabal; Roc Berenguer; Juan Melendez (2009). GPS and Galileo. McGraw Hill. ISBN 978-0-07-159869-9.
• Nathaniel Bowditch (2002). The American Practical Navigator – Chapter 11 Satellite Navigation . United States government.
• Global Positioning System Open Courseware from MIT, 2012
• Greg Milner (2016). Pinpoint: How GPS is Changing Technology, Culture, and Our Minds. W. W. Norton. ISBN 978-0-393-08912-7.

External links[edit]

• FAA GPS FAQ
• GPS.gov – General public education website created by the U.S. Government