GPS is just another fancy, expensive gizmo, right? Not really. I personally believe that a GPS unit belongs in the daypack or backpack of every person who likes to wander the wilderness. While some may think that a map and compass are all they'd ever need, truth is, many times it's just too much bother to accurately figure a map position correctly and a guesstimated location is used.

What IS a GPS Unit?

A small electronic device, a GPS will receive signals from several satellites (there are 30 GPS satellites, called NAVSTARs) and interpret those signals to calculate your position on the map. Theye are small and lightweight, and yes, battery powered; some people think this makes them bad news if the batteries fail. A few extra batteries won't weigh that much so I don't see this as a problem. Besides, as things have improved my new GPS runs 18 hours on two AAs, while my older unit ran 12 hours on three!

But a Person NEEDS a Map and Compass!

That is true. A compass in the pack, yes. A map? Of course! A GPS will give you information (more on this in a minute...) that you then use to pinpoint your location on a map. Plus, using a compass requires line-of-sight to some landmark (usually a mountain top), but I have been in at least two situations (prior to GPS) where there was no good way to figure out where we were! One of these times was after a snowstorm above tree line. The clouds obscurred the surrounding peaks and the trail was under snow. Another, more common situation, was being in a low area surrounded by dense forest and no landmarks in sight. It would have been very time consuming to climb a hill hoping for a view. Today's GPS SiRFStar III chips would have put us on the map, no problem. [The SiRFStarIII chip that reads the satellite signals is substantially better than previous chips, allowing a good signal read inside of a building! Dense canopy is not the problem it used to be, or still is with older units.]

As for using the compass to determine North: the newer GPS units point North, most require you to be moving, but now the newest units simply point North, period.

I have used a GPS for several years, confirming with every trip that it is a wonderful technology that shouldn't be dismissed as a toy.

This nifty little computer reads signals from satellites A,B,C, etc., calculates distance from each source by timing the signal, then uses triangulation to calculate the one place on Earth that is the resulting distance from satellites A,B,C, etc. As you move along, that position is indicated -maybe as a moving cursor, but certainly by a changing set of numbers that indicate both your location relative to the Equator, and location relative to 0°, the Greenwich Meridian, best displayed as Universal Transverse Mercator (UTM) numbers (more on that in a minute...), but if you prefer lat/long, it does that too.

Can you convert metric temperatures to Fahrenheit? How about millimeters and decimeters? If those are still giving you trouble, consider figuring out changes in location using degrees and minutes (parts of degrees. Ever wonder why a 7.5 minute map (7.5 minutes latitude by 7.5 minutes longitude) is rectangular, not square? Ever wonder, "7.5 minutes of what? Well drop lat/long for a minute (haha) and look at UTM:

The Beauty of the UTM Grid

If UTM numbers are new to you, they are likely going to become an "Aha!" kind of discovery; they are very much easier to use in figuring out just where the heck you are on the planet. The Earth is round. If this is news to you, you probably shouldn't be on this page. Because a circle contains 360° (units of angular measure, not temperature, it was easy to divide the Earth into 60 sections, each 6° wide at the Equator. Each section was divided north and south into 8° sections. Each section is then marked by a top to bottom meridian that permits referance left and right. Even if this sounds confusing, it works great when you can use meters as units of measuring instead of minutes and seconds. Let's look at a topo map:

Note the UTM Numbers Along the Edges of the Topo Map

Look along all sides of a topo map. Blue tick marks with 1- or 2-digit numbers followed by a larger-sized 2-digit number. These numbers are actually stripped of the three zeroes that could follow them. The numbers bottom to top represent the meters north of the Equator, or Northing; left to right are Easting numbers for the particular map section. In this picture the 4291 number indicates 4,291,000 meters north of the Equator.

If you were looking at your GPS and had a reading of 717 000 N and 4291000 E you would just need to locate that coordinate on the map:

Draw Some Base Grid Lines

Use a straight edge to draw a pencil line connecting at least a pair of marks for both northing (bottom to top) and easting (left to right). These base grid lines will let you extrapolate other lines when you are in the field.You can use the edge of the map itself: simply roll the opposite side of the map over and match it against the tick marks (see below). A sharp pencil line will be easy to draw with just that edge to guide you, useful if you are in the field without tools. Note that these lines will not be parallel to the map edges, rather they will angle in an attempt to be perpendicular to North as it is represented by the top center of the particular map section.

When you are in the field with a map that has been prepared with at least a few connecting lines, using the GPS is quite simple. Find the basic location and simply visualize the "fine tuning" or last three numbers of each coordinate. If you'd like, you can download a TopoGrid

Waypoint Planning Before You Go:

Preplan your waypoints by placing the 1:24 TopoGrid on your map with the Target Circle right on the intersection of two connected tick marks. The reason that there are extra squares on the overlay is to help you scoot over and up without drawing more lines. Locate your destination and simply count the grid squares, estimating fractional parts. Note the coordinates in UTM manner on the edge of the map. Enter that coordinate into your GPS.

Note: You can also use Topozone.com to get coordinates, or you might buy National Geographic Topo! software which will let you pinpoint a location and get is UTM coordinates and elevation.

Using the TopoGrid on the Trail:

To locate yourself on a map, first gather your data and lock it in. Write the coordinates on the edge of the map and give it a name. Place the overlay on your map and move the Target Circle to the closest intersecting grid lines. Move the overlay up (Northing) and to the right (Easting) from the base intersection, estimating the chunk fractions. Use a sharp pencil point to mark the map through the pinhole in the center of the Target Circle. That's pretty much where you are!

Note: Because of small errors that are off by simply the width of a pencil mark, coupled with the guestimating of the chunk fractions, topped by the slight signal error, you won't likely get the exact mark twice, but you will still be able to get sufficient accuracy to visually identify a place on a return trip; a buried treasure? Close! A lake? Right on the money! I have had excellent results with returning to specific locations.