GPS on cell phones is what people typically think about whenever taking a look at locating cell phones. GPS (Global Positioning System) using satellites is the most popular and more accurate technology of tracking. But, GPS demands satellites to be in direct line of site from the mobile phone. It doesn’t work really well indoors or in dense urban centers. If the smartphone is inside a structure, for instance your office, shopping center, or often riding in a car the signals might not reach the mobile phone. Sometimes dense cloud cover and heavy foliage impedes with signals. Some mobile phones can retain the last identified GPS location, others may not.
Much of the discussion dealing with GPS tracking, cell phone GPS and cell phone tracking software could be helped by a GPS Satellite primer.
GPS satellites broadcast signals from space that GPS receivers use to provide three-dimensional location (latitude, longitude, and altitude) plus precise time. GPS is an acronym for Global Positioning System and is a system that is composed of 3 main segments: Space Segment, Control Segment and User Segment.
The GPS Space Segment is comprised of twenty-four to thirty-two satellites that orbit the earth in medium earth orbit MEO. These satellites are referred to as the GPS Constellation, and they are orbiting once every 12 hours. They are not geosynchronous, they travel at over 7,000 mph. GPS satellites are solar powered but have battery backup for when they are in the earth?s shadow. They are positioned so that there are at least 4 satellites ?visible? from any point on earth. Small rocket boosters on each satellite keep them flying in the correct path. 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 offset and are in balance. This is the best location to position a stationary satellite. The earth rotates at about 1,000 miles an hour, and because of their high earth orbit the geostationary satellites need to move at about 7,000 mph to sustain position. This is just about the same speed as GPS satellites, but since communications 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 numerous dedicated and shared Ground Antennas and Monitor Stations that work together to ensure the satellites are working correctly and the information they send to earth is accurate.
The GPS User Segment consists of of GPS receivers taking the shape of devices 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 calculate location by precisely timing the signals transmitted by GPS satellites. This information includes the time the message was transmitted, precise orbital information (the ephemeris), and the general system health and rough orbits of all GPS satellites (the almanac).
Another method of determining device position is Triangulation or Mobile Location Services (MLS). Cell Tower Triangulation employs signal analysis data to compute the time it takes signals to travel from your cellphone to no less than three cell towers to determine position.
With Mobile Location Services (MLS), the GSM cell network provider utilizes triangulation techniques to determine the position of the cell phone, its accuracy is proven to be less than than that of GPS. MLS is further affected by the same issues as GPS in the sense of the barriers impeding signal quality and the density of GSM towers to help in the triangulation calculation. In rural areas position accuracy may be off as much as a mile.
An Introduction To Mobile Phone GPS Tracking
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