A Short Introduction To Cell Phone GPS Tracking

A lot of the discussion dealing with cell tracking, cell phone GPS and mobile phone tracking software could be helped by a GPS Satellite primer.

GPS satellites broadcast signals from space that GPS receivers utilize to determine three-dimensional location (latitude, longitude, and altitude) plus precise time. GPS stands for Global Positioning System and is a network that is composed of 3 main segments: Space Segment, Control Segment and User Segment.

The GPS Space Segment includes twenty-four to thirty-two satellites that orbit the earth in medium earth orbit MEO. These satellites are also known as as the GPS Constellation, and they are orbiting twice a day. They are not parked over one spot, they travel at over 7,000 mph. They are solar powered but have battery backup for when they are in the earth?s shadow. They are positioned so that at any given time there are at least 4 satellites ?visible? from any point on earth. Small rocket boosters on each satellite keep them properly positioned. The satellites last about ten years until all their fuel runs out.

GPS Satellites are not communications satellites. Geostationary or communications satellites are at a much higher orbit of about 22,300 miles above the equator. These satellites are used for weather forecasting, satellite TV, satellite radio and most other types of global communications. At exactly 22,000 miles above the equator, the earth’s gravitational force and centrifugal forces are canceled and are in balance. This is the best location to park a communications satellite. The earth rotates at about 1,000 miles an hour, and because of their high earth orbit the geostationary satellites need to travel at about 7,000 mph to sustain position. This is just about the same speed as GPS satellites, but since geo-synchronous satellites are 10,000 miles further away they stay in place relative to the earth.

The GPS Control Segment includes Master Control Station, an Alternate Master Control Station, and a host of dedicated and shared Ground Antennas and Monitor Stations that work together to make sure the satellites are working to specification and the data they send to earth is accurate.

The GPS User Segment made up of of GPS receivers taking the shape of cell phones and , laptops, in-car navigation devices and hand-held tracking units along with the people that use them, and the software programs that make them work.

GPS receivers sometimes take longer to become ready to navigate after it’s turned on because it must acquire some basic information in addition to capturing GPS satellite signals. This delay is sometimes caused if the GPS device has been turned off for days or weeks, or has been moved a significant distance while turned off for. The GPS must update its almanac and ephemeris data and store it in memory. The GPS almanac is a set of data that every GPS satellite transmits. When a GPS receiver has current almanac data in memory, it can acquire satellite signals and calculate initial location faster.

Another method of formulating handset location is Triangulation or Mobile Location Services (MLS). Cell Tower Triangulation makes use of signal analysis data to determine the time it takes signals to travel from the cellular phone to at least three cell towers to determine location.

With Mobile Location Services (MLS), the GSM cellular network provider uses triangulation techniques to estimate the location of the mobile phone, its accuracy is proven to be less than than that of GPS. MLS is further impacted by factors similar to GPS in the sense of the interference affecting signal quality and the density of GSM towers to help in the triangulation effort. In remote areas position accuracy may be off as much as a mile.

A Short Introduction To Cell Phone GPS Tracking