GPS technology was developed by the Defense Department for military use. It uses signals from a web of 24 satellites to plot a user's location anywhere on the planet in latitude and longitude. It also can be used to determine automobile or boat speed and direction or to give the distance between preprogrammed points. Many luxury cars are now available with the system. To mark a location, simply go outdoors and turn on the unit.
Satellite tracking is automatic.
Locking on to an initial location with the etrex took about a minute. After the unit warmed up, the time was cut to about 15 seconds. Many higher-end GPS models incorporate street and highway map software and have computer interface capacity. Most units marketed for hunting, fish or general outdoor recreation don't have those features. A GPS is now standard equipment for many tournament anglers, and virtually all pros use the technology to mark hot spots during practice rounds.