Over fifty GPS satellites such as this NAVSTAR have been launched since 1978. GPS satelliteEven fixed systems may use GPS, in order to get precise time. This antenna is mounted on the roof of a hut containing a scientific experiment needing precise timing.

Discover great deals on the many hard to find and one of a kind items available only on ebay!

GPS

The Global Positioning System, usually called GPS (the US military refers to it as NAVSTAR GPS - Navigation Signal Timing and Ranging Global Positioning System), is the only operational satellite navigation system. more...

HomeHome
ComicsComics
ComputersComputers
ElectronicsElectronics
BlackberryBlackberry
BluetoothBluetooth
DVD PlayerDVD Player
GPSGPS
iPodiPod
Metal DetectorMetal Detector
mp3 Playermp3 Player
MoviesMovies
TelevisionTelevision
ToysToys
Video GamesVideo Games


For a list of other proposed and partially developed systems, including Russia's RONASS and Europe's Galileo, see satellite navigation system.

Satellite Navigation Systems can be used for determining one's precise location and providing a highly accurate time reference almost anywhere on Earth or in Earth orbit. The accuracy of the GPS signal itself is about 5 meters (16 ft) as of 2005 and has steadily improved over the last 15 years. Using differential GPS and other error-correcting techniques, the accuracy can be improved to about 1 cm (.4 in) over short distances.

The GPS system was designed by and is controlled by the United States Department of Defense and can be used by anyone, free of charge. The GPS system is divided into three segments: space, control and user. The space segment comprises the GPS satellite constellation of at least 24 satellites in an intermediate circular orbit (ICO) . The control segment comprises ground stations around the world that are responsible for monitoring the flight paths of the GPS satellites, synchronizing the satellites' onboard atomic clocks, and uploading data for transmission by the satellites. The user segment consists of GPS receivers used for both military and civilian applications. A GPS receiver decodes time signal transmissions from multiple satellites and calculates its position by trilateration.

Daily management of the GPS satellite constellation is conducted by the 2d Space Operations Squadron at Schriever Air Force Base. The cost of maintaining the system is approximately US$400 million per year, including the replacement of aging satellites. The first GPS satellite was launched in February 1978, and the most recent launch was in September 2005. The oldest GPS satellite still in operation was launched in February 1989.

Technical description

The system consists of a constellation of at least 24 satellites in 6 orbital planes. The GPS satellites were initially manufactured by Rockwell and now manufactured by Lockheed Martin. The first was launched in February 1978, and the most recent was launched September 25, 2005. Each satellite circles the Earth twice every day at an altitude of 20,200 kilometres (12,600 miles). The satellites carry atomic clocks and constantly broadcast the precise time according to their own clock, along with administrative information including the orbital elements of their own motion, as determined by a set of ground-based observatories.

The receiver does not need a precise clock, but does need a clock with good short-term stability and the ability to receive signals from four satellites in order to determine its own latitude, longitude, elevation, and the precise time. The receiver computes the distance to each of the four satellites from the difference between local time and the time the satellite signals were sent (this distance is called a pseudorange). It then decodes the satellites’ locations from their radio signals and an internal database. The receiver should now be located at the intersection of four spheres, one around each satellite, with a radius equal to the time delay between the satellite and the receiver multiplied by the speed of the radio signals. Because the receiver does not have a very precise clock it cannot compute the time delays. However, it can measure with high precision the differences between the times when the various messages were received and hence use multilateration to accurately locate itself. This yields 3 hyperboloids of revolution of two sheets, whose intersection point gives the precise location of the receiver. This is why at least four satellites are needed: fewer than 4 satellites yield 2 hyperboloids, whose intersection is a curve; it is impossible to know where the receiver is located along the curve without supplemental information, such as elevation. If elevation information is already known, only signals from three satellites are needed (the point is then defined as the intersection of two hyperboloids and an ellipsoid representing the Earth at this altitude).

Read more at Wikipedia.org


[List your site here Free!]

Dual Electronics Xgps150 Gps ReceiverDual Electronics Xgps150 Gps Receiver $45.00 Samsung Galaxy S9 Sm-G960 - 64Gb - Gsm Unlocked Smartphone 9/10 - SbiSamsung Galaxy S9 Sm-G960 - 64Gb - Gsm Unlocked Smartphone 9/10 - Sbi $118.50
Delta Electronics Power Supply 750W | Gps-750Ab ADelta Electronics Power Supply 750W | Gps-750Ab A $50.00 Samsung Galaxy S10 Plus Sm-G975U 128Gb Black Fedex 2 Day At&T UnlockedSamsung Galaxy S10 Plus Sm-G975U 128Gb Black Fedex 2 Day At&T Unlocked $299.00
Samsung Galaxy A10e 32Gb 4G Lte Gsm Unlocked Android Smartphone BlackSamsung Galaxy A10e 32Gb 4G Lte Gsm Unlocked Android Smartphone Black $104.95 New ListingAmazon wholesale lot electronics & General Merchandise $200 valueNew ListingAmazon wholesale lot electronics & General Merchandise $200 value $5.50
Dual Electronics Xgps150A Multipurpose Universal Bluetooth Gps Receiver with WidDual Electronics Xgps150A Multipurpose Universal Bluetooth Gps Receiver with Wid $59.98 Liquidation Electronic and General Merch Lot. Great For Resellers.overstockLiquidation Electronic and General Merch Lot. Great For Resellers.overstock $125.00
Apple iPhone 7 Plus 128Gb Unlocked Smartphone - Very GoodApple iPhone 7 Plus 128Gb Unlocked Smartphone - Very Good $194.99 Samsung Galaxy Note 9 - Unlocked - 128Gb - Black - Unlocked - Smartphone - GoodSamsung Galaxy Note 9 - Unlocked - 128Gb - Black - Unlocked - Smartphone - Good $199.99
Dual Electronics Xgps150A Multipurpose Universal Bluetooth Gps ReceiverDual Electronics Xgps150A Multipurpose Universal Bluetooth Gps Receiver $134.90 Samsung Galaxy S10 128Gb Sm-G973U Fully Unlocked Smartphone New In Original BoxSamsung Galaxy S10 128Gb Sm-G973U Fully Unlocked Smartphone New In Original Box $312.00
Delta Electronics Gps-350Ab D H18 350W Switching Power SupplyDelta Electronics Gps-350Ab D H18 350W Switching Power Supply $15.99 Umidigi Bison Rugged Smartphone Waterproof Shockproof 128Gb Unlocked Cell PhoneUmidigi Bison Rugged Smartphone Waterproof Shockproof 128Gb Unlocked Cell Phone $152.99
Samsung Galaxy Note 10+ Plus Sm-N975U 256Gb Gsm Factory Unlocked Phone Open BoxSamsung Galaxy Note 10+ Plus Sm-N975U 256Gb Gsm Factory Unlocked Phone Open Box $429.99 Acr Electronics Gps Wearable Crew Tracker with Free Mobile App, 4 PackAcr Electronics Gps Wearable Crew Tracker with Free Mobile App, 4 Pack $155.00
i12 Pro Max Andriod SmartPhone 6.7 inch 12Gb Ram + 512Gb Romi12 Pro Max Andriod SmartPhone 6.7 inch 12Gb Ram + 512Gb Rom $134.22 Umidigi A7S 6.53" Smartphone with Infrared Temperature Sensor Unlocked 4150mAhUmidigi A7S 6.53" Smartphone with Infrared Temperature Sensor Unlocked 4150mAh $76.99
Umidigi Bison Rugged Smartphone Waterproof Shockproof 6Gb 128Gb Factory UnlockedUmidigi Bison Rugged Smartphone Waterproof Shockproof 6Gb 128Gb Factory Unlocked $179.99 Apple - A1858 - *Locked* Apple Watch Gps 38Mm ElectronicsApple - A1858 - *Locked* Apple Watch Gps 38Mm Electronics $55.00
Samsung Galaxy S9 | S9 Plus - 64Gb (Unlocked) Verizon At&T T-Mobile SprintSamsung Galaxy S9 | S9 Plus - 64Gb (Unlocked) Verizon At&T T-Mobile Sprint $149.98 to Cobra Electronics Cdr 840 Drive Hd Dash Cam with GpsCobra Electronics Cdr 840 Drive Hd Dash Cam with Gps $25.97
Lg G820 G8 ThinQ 128Gb Unlocked Smartphone - Very GoodLg G820 G8 ThinQ 128Gb Unlocked Smartphone - Very Good $124.99 Samsung G960 Galaxy S9 64Gb Factory Unlocked Smartphone - Very GoodSamsung G960 Galaxy S9 64Gb Factory Unlocked Smartphone - Very Good $134.99
Click to see more GPS items at www.ebay.com
Prices current as of last update, 09/12/21 3:44am.

Home Contact Resources Exchange Links ebay