# Tagged Questions

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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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 ...
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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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### 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 ...