Satellites drift slightly from their predicted orbits which contributes to errors.
Satellite and receiver clock errors in gps.
The more satellites a gps receiver can see the better the accuracy.
Every satellite contains an expensive atomic clock but the receiver itself uses an ordinary quartz clock which it constantly resets.
It can be quite large especially if the broadcast clock correction is not used by the receiver to bring the time signal acquired from a satellite s onboard clock in line with gps time.
Figure 1 illustrates the effect of neglecting the gps satellite clock offsets on the user position.
To compensate for the discrepancy the frequency standard on board each satellite is given a rate offset prior to launch making it run slightly slower than the desired frequency on.
Let the gps receiver receive signals from 4 satellites then there are two cases.
Gps coordinates calculated when satellites are clustered close together in the sky suffer from dilution of precision dop a factor that multiplies the uncertainty associated with user equivalent range errors uere errors associated with satellite and receiver clocks the atmosphere satellite orbits and the environmental conditions that.
A receiver s built in clock may have slight timing errors because it is less accurate than the atomic clocks on gps satellites.
Number of satellites visible.
Introduction gps has been widely used for precise positioning and na vigation applications.
As it is shown the satellite clocks reach up to more than math 150 math kilometres which leads to huge position errors.
The satellite s reported location may not be accurate.
Slight inaccuracies in time keeping by the satellites can cause errors in calculating positions.
This study utilizes undifferentiated phase data to calculate gps clock errors and to compare with the frequency of cesium clock directly to verify estimated clock errors by the method used in this paper.
In addition to the propagation er rors the receiver position accuracy availability reliabil ity and integrity of gps navigation solution are affected.
In a nutshell the receiver looks at incoming signals from four or more satellites and gauges its own inaccuracy.
To achieve this goal most studies have focused on the relationship between gps receiver clock errors and gps positioning precision.
The global positioning system has a clever effective solution to this problem.
One of the largest errors can be attributed to the satellite clock bias.
