A lot of the discussion dealing with Cell Phone Tracking and Phone-Location applications used to convert a typical smartphone into a Spy Phone could be aided with a GPS Satellite primer.  GPS satellites broadcast signals from space that GPS receivers use to determine three-dimensional location (latitude, longitude, and altitude) plus exact time. The acronym GPS represents Global Positioning System and is a network which is composed of 3 main segments: Space Segment, Control Segment and User Segment.

The GPS Space Segment incorporates twenty-four  to thirty-two satellites which orbit the earth in medium earth orbit MEO.  These kinds of satellites are also known as as the GPS Constellation, and they make an orbit twice a day.  They are not parked over one spot, they travel at over 7,000 mph. GPS satellites are solar powered but have battery power backup for when they are in the earth shadow. They are located so that at any given time one can find a minimum of 4 satellites visible from any point on earth.  Small rocket boosters on each satellite keep them correctly positioned.   The satellites last about a decade until all their fuel is exhausted.

GPS Satellites are not communications satellites.   Geostationary or communications satellites use a higher altitude positioned 22,300 miles above the equator.  Most of these satellites can be used for weather forecasting, satellite TV, satellite radio and many other types of global communications.  At precisely 22,000 miles above the equator, the earth’s gravitational force and centrifugal forces are balanced out and they are in balance. This is actually the perfect position to spot a communications satellite.   The earth rotates at about 1,000 miles per hour, and because of their high earth orbit the earth-synchronous satellites need to move at about 7,000 mph to preserve position.  This is roughly the same speed as GPS satellites, but because geo-synchronous satellites are 10,000 miles further away they stay in place relative to the earth.

The GPS Control Segment incorporates Master Control Station, an Alternate Master Control Station, and numerous dedicated and shared Ground Antennas and Monitor Stations that work well together to make certain the satellites are working correctly and the data they send to earth is correct.

The GPS User Segment incorporates of GPS receivers  represented by mobiles, laptops, in-car navigation devices and hand-held tracking products together with the individuals who use them, as well as the software programs that make them operate.

Tags

GPS Devices