GPS Used for Mapping
GPS provides a sound method for determining reasonably exact coordinates. If you want to know where you are standing, a simple hand-held receiver and a map can tell you. The obvious next step was to automate the map out of the process, and now GPS mapping systems are available for cars and computers.
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Identification
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The global positioning system (GPS) is the sole functioning example of a satellite-based navigational system in the world. It consists of an orbiting network of two dozen to three dozen satellites. While there are other countries (Russia, the European Union, India and China) all working on competing systems, none are operational.
How Does It Work?
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A GPS receiver works through receiving microwave signals from orbiting satellites. These signals contain the time of transmission and the position of the transmitting satellite. The receiver then derives information from these signals by analyzing the travel time of the signals and positions of the transmitting satellites, trilaterating its position. At least four signals are necessary for a good position lock using the GPS system.
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GPS Mapping in Cars
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In an car-based GPS device, the GPS coordinate data is put into a database of road map information, which allows your position to be indicated and continually updated on a visual map. The database and location information is also usually analyzed to provide directions to a set destination. Typical car GPS systems will also draw on data from the speedometer, combining speed with position data for a more accurate representation of location.
GPS Mapping Software
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There are a handful of software applications that allow for highly accurate maps based on satellite imagery to be downloaded into laptop computers. Hooking the computer up to a suitable GPS device then turns the laptop into a GPD mapping platform, combining the database of photographic maps with GPS location-finding. This can be a very useful feature in conducting surveys.
Problems with GPS
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GPS signals are relatively weak, so many forms of electromagnetic interference can disrupt one or more of the necessary microwave transmissions. Solar flares and other magnetic events can also disrupt the signals. As the system is dependent on four or more signals, this makes it very prone to interference. There are also man-made jamming devices.
Automobile GPS mappers have special problems all their own. The metal parts in automobiles, such as the frame and the wires of a window defroster, can combine to form an unintentional Faraday cage that blocks out the microwave signals. Also, car-tracking and GPS systems can lose their signal whenever they enter a tunnel or even go under an overpass.
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Resources
- Photo Credit Basic GPS receivers
