In a previous article we discussed how the GPS satellite system provided the user with location information. This article will look at the equipment and features that make a good GPS unit.

The first decision we need to make is where the GPS will be used. Handheld units have become more popular each year since they will work anywhere the user can take them. Handheld GPS units work on boats, in cars and in the woods. Permanent mount units are still extremely popular among boaters and fishermen because of the larger screen size. The final decision is up to you based upon your usage and budget.

When choosing a GPS unit, the most important feature is the receiver, or antenna. Be sure that any unit you purchase has a 12-parallel channel receiver. Remember, there are always up to 12 satellites above the horizon and available for your GPS unit to acquire. A 12-channel receiver allows your unit to acquire all 12 satellites at once, providing you with the most accurate position information.

Parallel channels are important since they allow the GPS to stay locked on to multiple satellites simultaneously. Older style receivers would only lock on to 1 satellite at a time and display the position information on the screen. With a parallel channel receiver, your displayed position is an average of the position information from as many as 4 satellites at once, which results in a much more accurate, seamless position display.

Once we have selected a GPS with a 12-parallel channel receiver, we need to start looking at some of the other features available. A GPS unit should be able to store at least 500 different waypoints. Waypoints are nothing more than exact positions on the earth, marked in latitude and longitude (more detail on waypoints will be coming in the next article of this series). You will want to save waypoints for boat ramps, tree stands, fishing spots and any other location you may want to return to in the future. A large waypoint capacity allows the user to save positions from many different locations in the GPS memory, and be able to recall them at any time.

Along with waypoints I prefer a GPS unit that also allows the user to save, display and view icons. Icons or "event markers" are simply symbols that are placed on the GPS screen to note the location of a particular event or landmark, such as boat ramps, fishing spots or gas stations. Very similar to waypoints, icons have a few differences that we will explore in a later article. Just be aware that they are available on some GPS units and are very effective for marking locations.

Another important feature is the number and type of "routes" the GPS can store. Most high quality GPS units can store up to 20 routes with 50 waypoints per route. A route is nothing more than a path to be followed. Inserting waypoints into a route in the order in which you wish to reach them makes this "path". Routes are invaluable when navigating around islands or swamps. Your GPS should have routes that are "reversible" or a feature called "track back". These features allow the user to enter 1 route and navigate it by starting at either end of the route as opposed to entering a separate route for each direction.

A feature I used for the first time last year is mapping. Without mapping, a GPS simply shows waypoints, plot trails and other information on a plain screen. With the mapping feature, all the GPS information is overlaid on a map of the area. Maps come in different degrees of detail, and the best will show cities, roads, points of interest, marinas, navigation buoys and other important information. Most GPS units that feature mapping include a CD-Rom with the mapping data, which must be downloaded into the GPS. More detailed mapping information is available from GPS manufacturers and after market companies that sell CD’s that contain topographical maps, lake depth contours, biking/hiking trails and other specific information. One great advantage to using mapping software that downloads into a GPS is the ability to obtain waypoints, create routes and plan a trip at the computer, then download all this information into the GPS.

Working in harmony with mapping is another critical feature-the ability to download all your waypoints, routes, trail and icons into your computer. This allows the user to sort the information and save each different area they travel to, fish or hunt as a separate file in the computer for future reference and modification. This feature also allows the user to print out waypoint information to keep as a hard copy, pass on to friends or record in a logbook.

As far as the outside of a GPS unit, screen size is probably the most important factor. My personal preference is to buy the largest screen I can find on a unit that meets the above requirements. Smaller screens are obviously harder to read, and several waypoints in the same area can become hard to distinguish from each other. Also look for a unit that has several buttons, as opposed to units that are strictly menu driven. The more features you can access with a single button push, the easier it will be to use the GPS to maximum effectiveness.

If you decide to purchase a handheld unit, there are several options that will make the unit more practical. If you are going to be using a handheld GPS in a boat, car or ATV you will want to purchase both a 12-volt power cord and some type of mounting bracket. These items will allow you to use the GPS without going through batteries. Another great option for handheld units is some type of weatherproof case for carrying and protecting the unit when outdoors.

Well there you have it-a quick look at the features you need to look for when purchasing a GPS. In the next article we will cover the basics of waypoints and icons and have a basic lesson on using latitude and longitude, determining waypoints and some software available to help both land and water based GPS users.