Up to this point we have only covered basic functions and features of a GPS unit. With this basic knowledge, we can now start talking about how to actually use a GPS unit on the water or in the woods.

The most basic use for a GPS is telling us where we are. By receiving signals from up to 12 satellites, the GPS can give us a very accurate reading of our current location. This information needs to be put into a format that is easy for the user to understand, and transfer to a chart or map. The most basic of these formats, and the most commonly used, is the latitude/longitude format.

GPS units will provide our location by designating a positions latitude and longitude. At one time or another we all learned basic latitude and longitude in geography class, but a little refresher never hurts.

Latitude is a measurement using lines that run in an east to west direction around the earth. These lines of latitude are also known as parallels, with the most well known parallel being the equator. The equator cuts the earth in half around its mid-section, and is designated as 0 degrees latitude. Our position is designated by how many degrees we are north or south of the equator. A common latitude designation would look like this N 45° 06.486. This would be read as North 45 degrees, 06.486 minutes, meaning our position is 45 degrees, 06.486 minutes north of the equator. There are 60 minutes per each degree, so the largest the minute designation can ever be is 59.999.

Latitude is designated from 0 to 90 degrees north or south of the equator. The North Pole is at 90 degrees north latitude and the South Pole is at 90 degrees south latitude. All other locations on the earth are somewhere in between. Since lines of latitude are parallel to each other, the distance between them never changes. The distance between each degree is about 69 miles. The distance between each minute is about 1.15 miles. The distance between each tenth of a minute is about .11 miles or about 580 feet.

The other half of a position reading is the longitude. The lines of longitude run "long ways" around the earth, in a north to south direction. The line of 0 degrees longitude runs through Greenwich, England (remember Greenwich Mean Time?). Longitude is stated as a distance of 0-180 degrees east or west of this line. The maximum measurement of longitude is 180 degrees west or 180 degrees east. The line of 180 degrees longitude, the International Date Line, runs through the middle of the Pacific Ocean, just east of Fiji and New Zealand. A common longitude reading would look like this W 083° 27.456. Read as West 83 degrees 27.456 minutes. As with latitude, longitude minutes cannot exceed 59.999.

Since lines of longitude follow the curve of the earth, the distance between them changes. Longitude lines are closest together at the poles, and reach their maximum separation at the equator. Distances in Lower Michigan are about 50.5 miles per degree, .84 of a mile per minute and about .08 of a mile per tenth of a minute.

Obviously knowing the latitude and longitude is very important in using our GPS to its full effectiveness. But how can we determine the latitude and longitude of a specific spot? There are four main ways that an outdoorsman will get position information.

The first way is perhaps the easiest. Simply go to the location you want to know the position of and read the position from the GPS. If you wish to use this position in the future, you may mark and save it in your unit as a waypoint or an icon (see your owner’s manual for specific instructions).

The second way is almost as easy and can be done anywhere. Hopefully you have fishing or hunting buddies who are willing to share their hotspots with you. All you need from a buddy is the latitude and longitude of a position and you can mark and save it as above. The only difference is that you will have to manually enter the latitude and longitude into the GPS unit.

The third way is perhaps the hardest to learn, but will become the most valuable to your success, enjoyment and safety in the outdoors. This method involves a map, a notebook, ruler and a set of dividers. Although the exact skills needed to use this method are beyond the scope of this article, I will give you a little background. Dividers, simply a tool used in navigation, are 2 legs attached at a common point. This instrument allows you to determine distance on a map. By using the dividers to determine an unknown points distance from a know position located on the map, we can arrive at the latitude and longitude of that unknown point. When that is done, write the point in your notebook and then manually enter it into your GPS. I use this method quite frequently when preparing for walleye tournaments on unfamiliar waters. By spending a night at my kitchen table with a map, dividers and my GPS, I can enter positions for boat ramps, fishing spots, hazards etc. By doing this at home, I can use all of my allotted pre-fishing time fishing instead of searching.

The fourth way is not available on all units, but can be a valuable tool, especially when used in conjunction with a GPS using a background map. Most units have what is called a cursor or "crosshairs". By moving this cursor to a desired location, you can save the cursor’s location as a waypoint and therefore know that point’s latitude and longitude.

In the past few years several companies have created computer programs with nautical charts and topographical maps. By loading these programs into your computer, you can simply move the computer mouse to the location you wish to get the latitude/longitude for, and the computer will automatically calculate your position. The best of these programs allow the user to save waypoints and icons on the computer and then simply download them into the GPS unit or download GPS information from the unit onto the program in the computer.

Some of the best programs I have used on the water are by Fishing Hot Spots and Navionics. For land based topographical information, MUCC has a great program available for the state Michigan. This disc, published by National Geographic is available from MUCC, and is capable of saving waypoints and downloading to many GPS models. All the topographical information such as roads, towns, elevation lines, rivers etc. is now available on compact disc for use in the computer. Using these programs before leaving home on a trip can save precious time, and help the user be much more prepared for their time outdoors.