Global Positioning System (GPS) is a satellite system that provides highly accurate location with the use of special GPS receivers and their augmentations. This accurate GPS data is of limited use by itself, unless it is coupled with a powerful visualization tool like the Geographic Information Systems (GIS). The GIS is a widely accepted visualization tool that presents data in a graphic form, which is a convenient and effective means of communicating complex information. These systems also have loads of relevant spatial and no spatial data existing as different layers of information that can be expressed as a map. When people talk about "a GPS," they usually mean a GPS receiver. The Global Positioning System (GPS) is actually a constellation of 27 Earth-orbiting satellites (24 in operation and three extras in case one fails). The U.S. military developed and implemented this satellite network as a military navigation system, but soon opened it up to everybody else.
     GPS-GIS integrated systems provide real-time meaningful location and status of the vehicles which can be used to plan trips, attend to real-time demands from consumers and monitor the traffic condition and driver behavior. These systems are an integral part of all modern fleet management systems and play a vital role in providing data for logistic planning and optimization in today’s increasingly competitive scenario.

How Location Tracking Works

Location tracking is not one, single technology. Rather, it is the convergence of several technologies that can be merged to create systems that track inventory, livestock or vehicle fleets. Similar systems can be created to deliver location-based services to wireless devices. Current technologies being used to create location-tracking and location-based systems include:

Geographic Information Systems (GIS) - For large-scale location-tracking systems, it is necessary to capture and store geographic information. Geographic information systems can capture, store, analyze and report geographic information.

Global Positioning System (GPS) - A GPS receiver, like the one in your mobile phone, can locate four or more of these satellites, figure out the distance to each, and deduce your location through trilateration. For trilateration to work, it must have a clear line of sight to these four or more satellites. GPS is ideal for outdoor positioning, such as surveying, farming, and transportation or military use (for which it was originally designed).

Radio Frequency Identification (RFID) - Small, battery-less microchips that can be attached to consumer goods, cattle, vehicles and other objects to track their movements. RFID tags are passive and only transmit data if prompted by a reader. The reader transmits radio waves that activate the RFID tag. The tag then transmits information via a pre-determined radio frequency. This information is captured and transmitted to a central database. Among possible uses for RFID tags are a replacement for traditional UPC bar codes. Wireless Local Area Network (WLAN) - Network of devices that connect via radio frequency, such as 802.11b. These devices pass data over radio waves and provide users with a network with a range of 70 to 300 feet (21.3 to 91.4 meters).

Wide-Area tracking
On a large scale, companies must track their vehicle fleets across the country or the world. GPS is the ideal tracking technology for tracking over large areas. To do this, every vehicle needs to be equipped with a GPS receiver. As the vehicle crosses the country, the GPS satellites track the truck's position. With GPS, the operator can request positioning at anytime. However, GPS is limited in smaller areas or indoors.

Local-Area and Indoor Tracking - A good example of where GPS would not be suitable for tracking items is in a warehouse or hospitals. The accuracy provided by GPS is not sufficient for such a small scale. Consider all of the medical equipment, wheelchairs, gurneys and even patients that need to be tracked. GPS is not a practical or cost-effective solution.

How GPS Works
Before we look at GPS Tracking in detail, we first need to establish what it is about GPS that makes this such a unique and useful technology. The principle behind GPS is that receivers are able to use the technique of “trilateration” to calculate their coordinates on Earth by measuring the time taken for signals from various satellites to reach them. The GPS software will account for any irregularities in the signal strength and clock differences between itself and the GPS satellite network by using signals from four separate satellites to improve accuracy. Usually the coordinates are then used to locate the GPS device on a map, which is either displayed to the user or used as a basis for calculating routes, navigation, or as input into mapping programs. For example, specific coordinates can be stored as waypoints allowing the user to retrace their steps by calculating the direction and distance to each waypoint that they have stored.

GPS Vehicle Tracking
This is particularly useful when using GPS units attached to vehicles which have distinctive identification such as chassis numbers. The same principle applies as for a GPS tracking device designed to be worn by a human, except that the GPS is integrated within the vehicular electronics.
Coordinated Tracking
This also opens up the possibility to allow for coordinated vehicle tracking, in which GPS tracking is used to share location information between several vehicles, all pursuing the same end goal. It is an approach that has been used successfully in conjunction with GPS fish finder units which help fisherman to locate, track and catch schools of fish.
Consumer GPS Tracking
Despite its’ hitch military and commercial fishing applications, as well as use in aviation GPS, the principal application of GPS tracking will be in providing an enabling technology to augment existing systems. These systems will include cell phones and vehicles, usually in conjunction with a central point of service designed to keep track of the location. The reason for this is to keep the cost of the actual GPS unit down as much as possible in order to supply a useful technology to consumers at an attractive price. Each of these 3,000- to 4,000-pound solar-powered satellites circles the globe at about 12,000 miles (19,300 km), making two complete rotations every day.


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