GPS has 21 Geo-Stationary Satellites and 3 Spare Satellites rotating in 6 Orbitary Motion at an angle of 55° inclined to the Equator at a height of 20,200 K.M from the Earth.
At least four GPS Satellites are visible orbiting over any point of the Earth.
In GPS each Satellite takes 12 hrs to go around the Earth.
A fix in space is determined by 3 Dimensions, e.g. Latitude Longitude and altitude (height above mean sea level), it can be calculated by a minimum of Four Satellites.
The Equipment suffers from the following Errors-
- Clock Error- Corrections up to 0.000 000 0001 second (One Nano Second) is made.
- Instrument/Receiver Error- The error caused by the GPS Receiver Instrument.
- Position Lines- Position Lines, when taken at a shallow angle causes an error in the calculated angle, causing a Position error, which is calculated by drawing position lines.
- Satellite Ephemeris- This occurs when the Transmitting Satellite is not in the position as calculated in the Orbit.
- Atmospheric/Ionosphere Layer Error- Radar Wave deflects on passing Ionosphere Layer, due to concentrated active ions in the Ionosphere.
- Satellite Clock Error- Satellite has Atomic Clock, whereas the GPS receiver has Crystal Clock. The Difference of clock causes Error.
Pseudo Range- is a Range that occurs due to Errors
GLOBAL ORBITING NAVIGATION SATELLITE SYSTEM
GLONASS has 21 Active Geo-Stationary Satellites and 3 Spare Satellites rotating in 3 orbitary motion at an angle of 60° to the Equator at a height of 19,000 K.M from the Earth.
Errors are same as of GPS.