Anyone who tries to compare GPS devices, can get overwhelmed by the large variety of receiver types and features. But if you have a clear idea of what you want from your GPS system, the required features will be obvious. And hopefully this brief GPS comparison guide will help sort out the best GPS system for you.

Although GPS receivers come in a number of different forms, they all share a basic navigation function. With the aid of the orbiting GPS satellites, the GPS equipment will locate exactly where it, and you, are. The various GPS devices mainly differ in their intended use, the features they include, and whether they're self-contained or part of a system.

Basic GPS Handheld Receivers
The simplest GPS equipment system is a hand-held GPS. Less than $100 will get you basic GPS handheld receivers that are just as accurate as more expensive models with added features. If you're looking for a portable GPS system for outdoor activities, like hunting, fishing, or hiking, a simple unit maybe all you need.

The main difference between basic GPS handheld receivers and more advanced GPS devices is what they show on their display screens. Advanced receivers can show electronic maps that have the same features as a paper map. But basic GPS units can only plot points on their otherwise blank screen. Your location is one of the points and the other points represent locations in the area that you've previously marked, called "waypoints". The receivers with electronic maps also display waypoints, but the waypoints are displayed on a map. However, even a simple handheld can provide:

• Your location, elevation, and estimated position error.
• The ability to plot your position and subsequent movement on its screen.
• The speed, direction, and distance you've traveled.
• GPS satellite information including the number accessed, their location, and signal strength.
• The ability to connect to a PDA or laptop computer with mapping software, and provide the location data.

GPS Handheld Receivers with Map Display
Like other modern electronics, as the prices of GPS handheld receivers have dropped, their features have expanded. And so now, most handhelds include the ability to display maps on their screen. Some GPS devices can only display a map which is built into the unit. These permanent maps are called "basemaps" and show the general points of interest for an area, such as major roads, rivers and airports.

More sophisticated models let you also display precision maps which are available from various sources. These electronic maps are detailed enough to make finding a city street address easy. The maps can be bought from both GPS device manufacturers and regular map makers. The data for the maps is downloaded and stored either in a GPS handheld's internal memory or a programmable data card.

GPS Watches
An offshoot of handheld GPS receivers is the GPS watch. A GPS wrist watch has the same functions as a basic handheld, but in a much smaller case. GPS watches have a display usually less than half the size of handhelds and their reduced memory means that fewer waypoints can be stored. And even the batteries usually have a shorter life than those for basic GPS handheld devices. So unless you're obsessed with size, a GPS watch is probably not your best choice.

GPS for PDA
Among the many accessories available for PDAs today, is the capability for GPS. You can get GPS for Palm or GPS for Pocket PC operating systems. Adding GPS functioning to a PDA can be done in two basic ways. Either you can connect a GPS receiver to the PDA with a cable or wireless, or use a PDA GPS receiver that mounts in a CompactFlash memory slot.

Even with separate GPS equipment, a PDA can add several important benefits. The typical PDA has a screen area that's 2 to 3 times larger than the average GPS handheld. And if you're trying to read the screen while traveling in a car, boat, or plane, this extra size can be a real help. The PDA also increases map storage capacity, even if the handheld can already display maps. Further, there are software navigation programs for PDAs that include voice commands to help guide you to your destination.

Laptop GPS
Laptop GPS provides further improvements to the benefits of PDA GPS. A laptop's large screen and increased memory allow for unlimited mapping capabilities. And similar to a PDA, laptop GPS is achieved by either connection to a separate GPS receiver, or by using a GPS PCMCIA card. A laptop is able to run the most sophisticated mapping software while having the clearest display. But at the same time, a laptop's larger size and higher energy requirements, limit where it's practical to use.

Advance Features
As the price and size requirements keep decreasing, GPS receivers will show up in more and varied electronic devices. One result may be an electronic equivalent of a swiss army knife with more functions than most people would ever need. But there are certain features that can be worth getting. For instance, if you need the highest location accuracy possible, look for receiver models that work with the Differential GPS (DGPS), or better still, the Wide Area Augmentation System (WAAS).