The main components of a GPS system are:

• GPS receiver (measures and logs data to hard disc);
• GPS antenna (required to track GPS satellites);
• GPS antenna cable (required to attach GPS antenna to GPS receiver);
• Power supply.

The user interface with the receiver is the front panel which contains a screen, a set of control buttons on the right, an alphanumeric keypad on the left, and a series of black buttons with which screen menu options can be chosen. Click here to see the Trimble 4000SSI front view. The rear of the receiver contains a number of sockets to which the antenna and external power can be connected. Click here to see the Trimble 4000SSI rear view. The primary power sources are two camcorder batteries inserted into slots in the base of the receiver. However, because of the limited lifetime of camcorder batteries, it is recommended that students always take an external power source (ie 12V battery) into the field. Click images for larger display.