What is Gps: Definition and 126 Discussions

The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. 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. Obstacles such as mountains and buildings block the relatively weak GPS signals.
The GPS does not require the user to transmit any data, and it operates independently of any telephonic or internet reception, though these technologies can enhance the usefulness of the GPS positioning information. The GPS provides critical positioning capabilities to military, civil, and commercial users around the world. The United States government created the system, maintains it, and makes it freely accessible to anyone with a GPS receiver.The GPS project was started by the U.S. Department of Defense in 1973, with the first prototype spacecraft launched in 1978 and the full constellation of 24 satellites 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. 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). Announcements from Vice President Al Gore and the Clinton Administration in 1998 initiated these changes, which were authorized by the U.S. Congress in 2000.
During the 1990s, GPS quality was degraded by the United States government in a program called "Selective Availability"; this was discontinued on May 1, 2000 by a law signed by President Bill Clinton.The GPS service is provided by the United States government, which can selectively deny access to the system, as happened to the Indian military in 1999 during the Kargil War, or degrade the service at any time. 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. GLONASS can be added to GPS devices, making more satellites available and enabling positions to be fixed more quickly and accurately, to within two meters (6.6 ft). China's BeiDou Navigation Satellite System began global services in 2018, and finished its full deployment in 2020.
There are also the European Union Galileo positioning 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.When selective availability was lifted in 2000, GPS had about a five-meter (16 ft) accuracy. GPS receivers that use the L5 band can have much higher accuracy, pinpointing to within 30 centimeters (11.8 in). 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.

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  1. T

    How Critical Are Relativistic Effects in GNSS Accuracy?

    I was curious about the use of relativity in GNSS (GPS) systems (since I only know very basic relativity but I wouldn't mind having a good excuse to learn more... :biggrin:), and I've found some conflicting results. Some say that the relativistic variations in satellite clock speed have a HUGE...
  2. E

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    Hello everyone, Although I am not a physicist, I have been trying to understand the relativity effects on GPS clocks. It's seems pretty logic, however I've stumbled upon on a specific issue: Given a atomic clock without any kind of relativistic adjustment, if the GPS clock is running...
  3. L

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  4. A

    Controlling a Robot with GPS: What You Need to Know

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  5. E

    Do GPS Clocks Really Run Slower Than Earth Clocks Due to Time Dilation?

    I had such success with all your answers to my last SRT question here I’ll try another. The LT seems very symmetric. To the observers in each frame, the other’s clocks appear slower, etc. Is that true for out GPS satellites? If we ignore the GRT effect of speeding up their clocks, I think it is...
  6. Q

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  7. M

    How GPS receivers work (simple and advanced explanations of trilateration)

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  8. J

    What relativistic effects to GPS receivers compensate for?

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  9. F

    Can a Garmin GPS be turned into a DIY tracking device?

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  10. G

    Accuracy of a GPS receiver by comparing with post-processed DGPS data?

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  11. L

    CanSat Help - calculating its path without gps

    Hi there I am a Maths major student with little physics and engineering background. I'm a member of my university's space and astronomy club and we're building a CanSat as a project ( http://en.wikipedia.org/wiki/CanSat ). I have been given the task of mapping the Cansat's coordinates without...
  12. M

    Misc. Do it Yourself Differential GPS

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  13. J

    MATLAB How can I overlay a GPS track on a city map using GIS software?

    I have a GPS track I'd like to plop on top of a map. The region of the track is very small, no bigger than the area of a city. I also have a bunch of shape files to build up a map of the city with all the buildings, roads, etc. in separate shp files. Although the shape files actually contain...
  14. C

    Small GPS devices with long battery life

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  15. M

    Which GPS receiver is most accurate for the iPhone 4S?

    How accurate does the GPS on your phone tend to be? When I'm outside, under good conditions I can see impressive accuracy, especially considering the precision of the measurements. I walked to the left of a building this afternoon, out by the parking lot. The phone thought I was positioned...
  16. K

    GPS, irregular area under graph project

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  17. Ivan Seeking

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  18. E

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  19. R

    3 GPS Satellites & Receiver Clock Synchronization

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  20. A

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  21. I

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  22. T

    Need method for trilateration of 3 GPS satellites

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  23. Greg Bernhardt

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    Today marked a big win for privacy advocates. *The U.S. Supreme Court handed down a ruling on the question of whether it was Constitutional for police to attach a GPS tracking unit to someone’s vehicle without their consent, and without … Continue reading...
  24. G

    Calculating GPS Accuracy Using Special Relativity and General Relativity

    Hello, I need to calculate how accurate a GPS system is using only Special Relativity and a very basic knowledge of GR (without tensors...which is limited). I'm not sure where to begin however... where does the uncertainty in the measurement come from? How can I calculate the size of the...
  25. haael

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    To detect gravitational waves, we set up some probe masses in laboratories far from each other and measure distance between them. Why not use GPS satellites for that? I mean: they have precise atomic clocks, they constantly measure their position relative to each other and they are as far away...
  26. S

    GPS & Relativity: Position Error Lower Than 38000 Feet?

    I was watching QI http://www.youtube.com/watch?v=gU7McFm_cKQ&t=7m09s and prof Brian Cox said that time runs roughly 38000 ns per day faster on GPS satellites than on the ground. From that he concluded that since light travels roughly 1 foot per nanosecond, GPS would generate a positional...
  27. R

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  28. F

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  29. G

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  30. G

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  31. V

    Gravity and Time Dilation: How Do They Relate?

    sattelite tick slower than an Earth bound clock. Let's say an atomic clock. From what I've gathered so far, the clock aboard the GPS sattelite ticks slower The sattelite is in free fall so the clock aboard the sattelite is in zero G. Is the zero G condition the only condition that cause...
  32. A

    GPS in cameras and phones creates privacy issue

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  33. D

    What is the purpose of the fourth satellite in GPS navigation?

    Hey all, im doing a individual info search on GPS. i can understand everything (well its just a basic overview of GPS) but the one thing i can't get my head around is why the need for a fourth satellite? i know it corrects the timing as the receiver does not have an atomic clock. I've read 4 or...
  34. R

    GPS - Doubt regarding RMC speed value in NMEA files

    I am afraid that this is either too specific and\or that this is in the wrong forum (if the latter is the case, if moderators could change this, I'd appreciate :). I'm trying to do an application that uses the GPS data that comes from NMEA files. On a particular sentence (RMC) there is a value...
  35. J

    Designing a GPS Device with Optimal Connectivity for Indoor and Outdoor Use

    "GPS" device & connections Instead of using the satellites like Google Maps, is it possible to come up with a device that any device, such as mobile and laptops can connect and communicate with the device? In other words, let say Harvard campus. We know its campus is very large in terms of...
  36. I

    What Are The Basic Physics Principal For GPS, TV and Radio?

    I'm having to do a project and i got to do a detailed presentation describing and explaining the basic physics principals for gps's, tv's and radio. Each section has to be around 3-4 minutes of explanation. Im hitting a big rut with trying to find research for it. Also I am in gr.12 physics...
  37. DaveC426913

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  38. P

    Is GPS the only practical application of General Relativity?

    I guess GR is also needed to accurately coordinate space flight, but I highly doubt without GR the space shuttle will have any problem finding its way back home. Gravitational lensing doesn't count as practical application. Maybe a subject with even fewer applications is quantum chromodynamics...
  39. mugaliens

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    Actually, it's not GPS itself which is at fault, but the software or those who use them. http://news.yahoo.com/s/ap/20100102/ap_on_hi_te/us_stranded_motorists" blindly followed their GPS on a shortcut through mountain ranges in the winter and became stuck in the snow. I find that easy to...
  40. C

    Why does time dilation only affect GPS satellites in one direction?

    Can anyone answer this? GPS satellites are preprogrammed before launch due to relativistic effects mainly time dilation and gravity. Yet, once in orbit, the satellite should view the Earth frame as "moving" and thus apply time dilation to the Earth frame meaning the Earth clocks should beat...
  41. C

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  42. DaveC426913

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    Anyone here into sailing or boating? I haven't left my mooring yet, been testing it at anchor but my new Humminbird 383 insists I'm pointing NE when I'm actually pointing SW. It changes its mind every so often, occasionally it's correct, but seems to return to this position. I've left it...
  43. C

    GPS Pseudo-range and Positioning

    I am trying to see how a GPS works by analyzing the data it collects. Basically, I have the pseudorange, satellites positions and also the GPS receiver location data I got from a GPS, and I was expecting to reproduce the positions reported by the GPS to high accuracy by solving the pseudorange...
  44. T

    Energy used during vehicle trips from GPS data

    Hello, I have recently found an urge to understand the amount of energy that I use while driving. I would like to be able to record tracking data via GPS in a GPX format, and then calculate the amount of energy that would be used to perform the same trip using various vehicle models. I...
  45. M

    Find all nonisomorphic abelian gps

    Homework Statement - List all nonisomorphic abelian groups of order 2^3 3^2 5 Homework Equations The Attempt at a Solution - Z_2^3 * Z_3^2 * Z_5 = (iso) Z_360. Z_2^3 * Z_3 * Z_3 * Z_5 = (iso) Z_3 * Z_100 . . . I know , but why Z_360 , Z_3 * Z_100 are nonisomorphic to 2^3...
  46. S

    Are There GPS Devices Small Enough to Install Inside a Laptop?

    Is there anyone who knows of a tracking device small enough to install inside a notebook/laptop. Apart from RFID tags which only track within a given range. A GPS device that would track an asset as it were a car
  47. C

    Interference : GPS Transmission

    The GPS (Global Positioning System) satellites are approximately 5.18 m across and transmit two low-power signals, one of which is at 1575.42 MHz (in the UHF band). In a series of laboratory tests on the satellite, you put two 1575.42 MHz UHF transmitters at opposite ends of the satellite. These...
  48. Loren Booda

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    How does the Global Positioning System compensate for mapping the irregular surface of the Earth relative to its center of mass?
  49. D

    How do GPS devices determine your position?

    Hello i need help regarding GPS devices and the physics that goes into them. This may include, how the signal travels from source to GPS. Refractional waves and atmosphere interference. The process that goes into GPS devices in finding ur position. (Physics Based) thank you =]
  50. D

    GPS Physics: Reflection & Signal Acquisition

    hello i was wondering the physics that goes into transmitting waves such as: reflection etc.. To achieve a GPS signal, as well as the process of achieving it.
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