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Questions tagged [gps]

The Global Positioning System is a global satellite navigation system created and maintained by the United States. The Galileo project is a European Union global satellite navigation system serving the same role.

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Number of GPS satellites required to give 100% coverage

I am a Belgian school student in sixth grade of secondary school (the Belgian equivalent of High school). Together with two class mates we were assigned to write some kind of essay about the Global ...
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Estimating a new latitude/longitude using 2 previous datapoints and elapsed time: proofcheck help

I'm doing this all in code, could anyone with a better understanding of physics than mine read over my method to make sure my principle is sound? I have a device constantly sending a timestamp and it'...
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4k views

Why isn't the GPS location calculated from the Schwarzschild metric?

The GPS uses the flat space light propagation formula to calculate the distance from the source (the satellite) to the receiver (observer on Earth): $$ d=c \cdot \Delta t$$ where $c$ is the speed of ...
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Would Earth clocks tick faster than a clock on a GPS satellite if we disregard gravitational time dilation?

If we disregard the time dilation caused by a GPS satellite being in lower gravity, would earth's clocks tick faster or slower from the satellite's perspective? Edit. From earth, we understand that a ...
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How do I calculate time dilation on GPS satelites due to Earth's mass?

I found this answer which gives as the formula $$T_2 = \frac{T_0}{\sqrt{1-\frac{2GM}{c^2 R}}}$$ that should result in the time $T_2$ passed on a GPS satellite while $T_0$ seconds pass in the center ...
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248 views

Electromagnetic Waves and GPS

If the global positioning system functions through radio waves, but radio waves are reflected in the ionosphere, then how do these electromagnetic waves reach the satellites?
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GPS Satellite at GEO Orbit [duplicate]

I know the relativistic correction parameters for the current MEO orbit for GPS. We are considering placing some GPS SVs in a GEO orbit which would involve a different set of relativistic corrections ...
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Relativity Correction for GPS at GEO Orbit [duplicate]

What would be the relativistic corrections for a GEO GPS Satellite - analogous to the 7 microsecond slowing and the 45 microsecond speeding up due to gravitational redshift?
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Why do GPS satellites care about Earth clock at all? (relativity)

Many online resources make grandiose claims about how GPS would be useless without relativistic corrections. Specifically, they outline that satellite clocks runs slower by 7μs/day due to special ...
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1answer
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How are GPS corrected for special/general relativity?

I was looking for the equations that are used by the GPS receiver to calculate its position and time correction (bias). By looking at the Navigation Equations on Wikipedia, I don't see any account for ...
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Would GPS work in a (locally) newtonian universe?

Often, when there are question on why fundamental research makes sense or is neccesary, I've seen answers like "GPS is used everywhere today, and it wouldn't work without relativity". Of course, if ...
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What is the current limiting factor for GPS clock synchronization precision?

In the (slightly dated) paper 'Quantum Clock Synchronization Based on Shared Prior Entanglement' [R. Jozsa et al., Phys. Rev. Lett. 85, 2010 (2000)], the authors describe the GPS synchronization ...
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How many caesium clocks are there on each GPS satellite ? Is there any other atomic clock on-board?

I am trying to find how many caesium atomic clocks are carried by each of the GPS satellites. And whether the satellites also carry other atomic clocks, such as rubidium or hydrogen clocks.
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If relativity is symmetric, do the satellites in the GPS system see the earthbound clocks as running slow due to relativistic time dilation?

If relativity is symmetric, do the satellites in the GPS system see the earthbound clocks as running slow due to relativistic time dilation? How much slower does the satellite see the earthbound ...
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934 views

Can GPS signals penetrate steel in the thickness of few centimeters?

Can GPS signals penetrate steel in the thickness of few centimeters? Can they penetrate even thicker steel or other materials than steel (as well as steel?)?
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How are three satellites sufficient to find a unique point in GPS? What happens in case of an overlap? [closed]

Is it because the 2nd and 3rd satellites' centres are collinear? How is satellite overlapping avoided? If not avoided then what happen to the signal sent from an overlapped satellite?This is just a 2D ...
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1answer
5k views

Why GPS signals doesn't work indoors but mobile signal does?

GPS signals 1000-1500MHz range doesn't seem to work indoors (sometimes it does) but cell phone signal 1800/900 MHz works? Can mobile phone signals penetrate solid matter like homes/offices etc?
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Electromagetic Waves Behavior

In the radio spectrum, higher frequencies attenuate faster. Also, in my understanding, higher frequencies travel more along line of path. Lower frequencies can penetrate through solid materials but ...
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115 views

light-time correction in GNSS service

I have tried to use C/A code for single point positioning with light-time correction. I found the below equation for that.Can any one explain how to use this equation for light-time correction? $$\...
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Do relativistic phenomena affect communication with satellites?

Communication with satellites certainly requires knowing the speed of light. Beyond having that magic number, do relativistic phenomena affect communication with satellites? For example, would one ...
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1answer
93 views

In what way has GPS had an impact on our understanding of physics?

I've been reading about the effects GPS has had on our society with the February launch of a IIF Satellite and I was wondering if launching GPS satellites and the actual GPS satellites have lead to ...
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Does barometer improve gps position accuracy?

It is clear that a barometer is more accurate in measuring altitude than GPS. However is it true that the barometer improves GPS position accuracy? Would be a GPS device and a GPS+barometer device ...
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1answer
121 views

How does GPS on an airplane report a 100 km error?

On a flight across Europe, I took my iPhone out to see if the GPS can find my position. I was sitting away from a window, so reception would have been bad. I wouldn't have been surprised to get no ...
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Why would a modern smartphone not work if the theory of general relativity hadn't been discoverd? [closed]

My teacher told me that todays smartphones wouldn't work if the theory of relativity hadn't been discovered, but he didn't explained why.
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Time Synchronization Between 2 GPS Controlled Rubidium Clocks [closed]

I have 2 GPS Controlled Rubidium Clocks I need it to be synchronized to one another to the level of a microsecond. My question is what is the max phase (ns) allowed from the clock's input 1pps, for ...
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I don't see that general relativity is really needed for GPS to work correctly [duplicate]

From what I understand, GPS localization is based on the difference in the reception time from the time of emission of a signal from different GPS satellites whose positions are known. For this we ...
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1answer
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are GPS points versus an area?

I have a $\text{i2c}$ GPS module I got working yesterday, and here are my co-ordinates. Latitude: 44.901354999999995 Longitude: -68.97112333333333 What I am having trouble figuring out is that ...
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Can a GPS system detect the decline in the rotational velocity of the Earth?

From Wikipedia: Rotation in Angular Velocity of Earth Earth's rotation is slowing slightly with time; thus, a day was shorter in the past. This is due to the tidal effects the Moon has on Earth's ...
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Tidal effects in Global Positioning System?

Are tidal effects from the Sun and/or Moon taken into account in GPS systems? More broadly, is the heliocentric system used somehow in GPS?
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1answer
481 views

A question about the physics involved in tracking satellites such as those used in the GPS system [duplicate]

I know that besides the effects of Newton's theory of Gravitation on the satellite's motion, one has to take account of the retardation of the satellite's clocks when compared to earth-fixed clocks. ...
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3answers
228 views

How and when are the relativistic corrections applied to GPS satellites?

It is known that there is a need to correct the onboard clocks to reduce the time difference from 38μs to 50ns. Where is relativity playing its role here? Why cant the clocks be simply synchronised ...
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1k views

How often does a GPS receiver receive microwave signals from satellites?

I'm just finishing up a report on the mathematics of GPS, but I'm not sure how to determine how often a GPS receiver actually receives data from the satellites. If a satellite send out its microwave ...
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1answer
114 views

Time flow difference for satellites [duplicate]

Clocks in satellites have to be adjusted due to the effects of relativity; but does time for satellites (GPS) flow slower, due to the relative motion, or faster, due to the weaker amount of ...
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345 views

Counter-rotating flywheels for “flying saucers”

In 1974, while living in a farmhouse next to the Johns Hopkins Applied Physics Laboratory in Laurel, MD, I became obsessed [to the total consternation and perturbation of my wife, of that time, and my ...
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Point of rotation appears as an ellipse when calculated from gps coordinates

First question here. Feel free to write if I posted in the wrong place. While rotating a ship as accurately as we can around some point within the ship, we can calculate the point of rotation from ...
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1answer
879 views

GPS Satellite - Special Relativity

I'm going through an old relativity assignment, and I've been asked to calculate the time dilation for a satellite which orbits the earth in 12 hours at 26000km from the surface, and travels at a ...
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1answer
386 views

What will happen when Russia shuts down the GPS stations? [closed]

Russian officials are seriously talking about shutting down US GPS ground stations within their borders and Deputy Prime Minister of Russia tweeted on the subject. What will happen to the GPS? My ...
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What is the longest distance over which echolocation is effective?

Some animals, most notably bats, use echolocation in order to navigate and detect the location and size of objects and prey. This usually takes place over short distances. What are the theoretical ...
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1answer
107 views

What is the constant $K_1$ in these orbital equations?

I want to compute the derivatives of argument of periapsis and longitude of the ascending node of the orbit of a GPS satellite from the following formula. $$\frac{d\Omega}{dt} = -K \cos{i} \\ \frac{...
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Observations used to derive orbital and timing information required for GPS satellites

Although I have studied GPS receiver position finding procedure in some detail, I am struggling to find enough information to allow me to deduce how the essential highly accurate orbital and time ...
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993 views

GPS Working Principle [closed]

Hand-held GPS units in modern phones identify your location by (A) transmitting their location and time to GPS satellites. (B) receiving location data of GPS satellites. (C) receiving ...
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How to keep the clock of a spaceship synchronised to the clock of an observer? [duplicate]

I read that the clocks of GPS satellites seem to run slower than the clock of stationary observer, because of their speed (special relativity) and seem to run faster than the clock of stationary ...
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1answer
324 views

Gravitational resonances for satellites

I read on the website of European Space Agency that the altitude of Galileo satellites, which is 29600 Km from the center of the Earth, is chosen to avoid gravitational resonances so that station ...
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1answer
894 views

Cancelling special & general relativistic effects

We know that for a GPS we need to make a correction for both general and special relativity: general relativity predicts that clocks go slower in a higher gravitational field (the clock aboard a GPS ...
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1answer
179 views

Is GPS time measuring the proper time on the mean sea level or the GPS station itself?

LeapSecond.com states: Global Positioning System time is the atomic time scale implemented by the atomic clocks in the GPS ground control stations and the GPS satellites themselves. Does GPS time ...
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3answers
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That 10km/day error predicted if GPS satellite clocks not corrected for relativity

Some authorities have stated publicly and without explanation that if the theories of Special and General Relativity were not taken into account in the design of the GPS (by building the satellite ...
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2answers
536 views

Over what distances can one send/ receive from a GPS chip implant in a dog?

I am not into all the tech details of communication via RF with implant chips (tracking chips) and so would like to ask how the known atmospheric pertubations of shortwave radio affect the distances ...
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4answers
1k views

How do GPS devices work?

I have GPS in my phone but I have only a very rough idea of how it works. I have checked the Wikipedia article but that gone over my head (I can not understand that maths and other strange stuff there)...
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Special Relativistic approximation to GR

Some time ago I was talking to a professor in college about some of the fundamental aspects and origin of General Relativity. I was surprised to learn, in fact, that a pretty good approximation to GR ...
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4answers
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Why GPS is at LEO?

Why GPS/GLONASS/Galileo satellites are on low earth orbit? Why geostationary orbit is so bad? Sattelites might be placed there 'statically' and more precise... The only problem I can see is ...