GPS on cell phones is what people usually think about whenever reviewing tracking smartphones. GPS (Global Positioning System) using satellites is the most common and more accurate method of tracking. Yet, GPS must have satellites to be in direct line of site from the cell phone. It doesn’t work really well indoors or in dense urban centers. If the cellular phone is inside a structure, for instance your office, shopping center, or often riding in a car the signals might not get to the smart phone. Sometimes dense cloud cover and heavy trees impedes with signals. Some cell phones may hold on to the last identified GPS position, others might not.
Much of the discussion surrounding GPS tracking, mobile 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 system that is composed of 3 primary segments: Space Segment, Control Segment and User Segment.
The GPS Space Segment made up 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 twice a day. They are not geosynchronous, but rather move at over 7,000 mph. They are solar powered but have battery backup for when they are in the earth?s shadow. They are placed 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 flying in the correct path. The satellites have a lifetime of about 10 years until all their fuel runs out.
GPS Satellites are not communications satellites. Geostationary or communications satellites are parked in space 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 equilibrium. This is the ideal 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 keep position. This is just about the same speed as GPS satellites, but since earth-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 numerous dedicated and shared Ground Antennas and Monitor Stations that work together to make sure the satellites are functioning correctly and the data they send to earth is accurate.
The GPS User Segment made up 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 function.
GPS receivers compute position by precisely timing the signals sent by GPS satellites. This data 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 way of calculating cell phone location is Triangulation or Mobile Location Services (MLS). Cell Tower Triangulation makes use of signal analysis data to compute the time it takes signals to travel from the cellphone to a minimum of three cell towers to calculate position.
With Mobile Location Services (MLS), the GSM cell network provider utilizes triangulation algorithms to try to pinpoint the location of the mobile phone, its accuracy is proven to be much worse than that of GPS. MLS is further impacted by factors similar to GPS in the sense of the barriers affecting signal strength and the density of GSM towers to assist in the triangulation calculation. In rural areas location accuracy may be off as much as a mile.
A Quick Introduction To Cell Phone GPS Tracking
No comments:
Post a Comment