GPS ,Global Positioning System, is a navigation system that utilizes 24 orbiting satellites to fix your position on earth. It is accurate to within in 50 feet for the customer units. GPS units vary in size and can be large commercial, auto , or handheld.
They are very lightweight and meant to be carried easily. The screens are smaller and come in color or monochrome.They resemble a walkie talkie in size and structure. The battery life can vary between 15 to 35 hours. Most are loaded with North American maps. The real power is in the loaded maps. Handheld GPS units rely on waypoints for navigation. A waypoint is just a map marker. The loaded maps can be very detailed.

Some points to consider before you purchase a handheld GPS unit

1. Make sure it has at least a 12 channel parallel receiver system
2. Check the comfort in size and weight for your practical use
3. Maximum waypoint inputs preferably over 500
4. At least 20 route memory capacity
5. Waterproof is worth the extra charge
6. Screen size and mapping features