It is GPS technology that is used to track individuals on home arrest, to trace missing pets, stolen vehicles, and missing people. Small systems can be incorporated into pet collars and wristwatches. As long as receiver is active, it can be found.

Marine and aviation GPS units are sophisticated and specialized. The principles involved are same as any standard system; software is much more highly developed.

Any fisherman, who is using a fish finder on his boat, is using a GPS that is enhanced by sonar and tracking devices. Units have been developed for use on float tubes also -– as GPS technology advances, systems become more and more compact and their uses more and more extensive.

If you are considering purchasing a GPS, make sure that it can be updated easily. This is especially true if you buy a multi--function GPS or one that is used where conditions change regularly. An in--vehicle GPS soon loses its usefulness if it is not updated as road systems change.

Updates vary according to device being used. They can come in CD/DVD packages or as computer downloads. The user can purchase maps specific to area in which GPS will be used or a range of maps and routes. These are available from GPS software companies who will charge proportionally to sophistication of software.

GPS units vary in price according to their usefulness. It is possible to buy units for less than one hundred dollars to units costing more than one thousand dollars. What your needs are will be a factor in cost of your unit. If you are a backpacker then portability is a major consideration. If you are a trucker, you need to be able to find a delivery point as quickly and conveniently as possible. Whatever device you go for, cost is generally related to quality. Buy best you can afford.