Space Exploration Stack Exchange
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Questions tagged [gps]

Questions regarding the Global Positioning System's satellites and uses.

105 questions
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What is required to make GPS signals available indoors?

GPS satellites don't transmit strong enough to reach indoors, through the roofs and walls of buildings, like cell phones do. GPS signals that enter buildings through windows are unreliable since they often have bounced and thus give the wrong…
LocalFluff
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Would a GPS receiver with an onboard atomic clock only need 3 satellites to determine position?

GPS receivers need four satellites to determine their position and time. They provide a receiver with data that is fed into four equations. Three equations are solved (simultaneous with the fourth) to get position. The fourth equation solves for the…
chessofnerd
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How does GPS module gets time even before a fix?

I have a GPS module which outputs NMEA messages at 1Hz. In the data sheet it is mentioned that at cold start, it will get a fix in 29s. I run it cold start and indeed it gets the fix in 29th second. However in around 12 seconds, I start getting the…
Hassan
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Precise timing using GPS

Looking at https://gssc.esa.int/navipedia/index.php/GPS_Navigation_Message and other websites, in order for a satellite receiver (which doesn't have other means of getting precise GPS time) to determine precise GPS time, after it's determined its…
Randy
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If the pseudorange is not fixed, how does a receiver lock/fix onto a satellite signal?

If the satellite moves around the orbit at a velocity, the pseudorange between the receiver and the satellite should be changing right? If so, how does a receiver lock onto a satellite signal if the propagation delay keeps changing as…
newlearner
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Why using internet connection speeds up the GPS positioning?

I noticed that when I activate my cell phone internet connection, I get my GPS position much faster. What does the internet connection provide for the GPS receiver ?
Yahya Aouled Amer
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How is the GPS signal transmission time encoded in the GPS signal?

I am trying to really understand how GPS works, to be able to "explain it to my grandma" level of understanding. One key aspect that I can't find an answer to is: how is the GPS signal transmission time, as registered by the on-board atomic clock,…
largehadroncollider
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GPS PPS stable signal

My question concerns the GPS NMEA reading data about PPS signal. Is there any way to know via software using NMEA that the GPS PPS signal provided by its outport is already synchronized with the one of the satellite? Does it mean that when the GPS…
peter
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What are RAIM Service Outage, RNP and EnRoute on GPS DOP maps? What does the red line mean?

Reading @Antzi's question about GLONASS and GALILEO led me to the NTSB's Current GPS SPS Navigation Service Display or SPS PDOP (dilution of precision) map for GPS. Each time the map updates (every few minutes) the contours change, and there are…
uhoh
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Would GPS work above the GPS satellites?

If a rocket carrying a GPS device ascended above the height of the orbit of the GPS satellites (about 20,000km), what height would the GPS device report? Would it keep reporting the correct height as it passed through the orbit height, or would it…
Bohemian
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