I can be pretty clever indeed at dreaming up excuses to buy new toys. When our major Canadian ham radio outlet advertised a sale on Garmin GPS receivers, I reasoned that I really should buy one to single-handedly help them stay in business! It was practically my civic duty. Perhaps almost as far-fetched, I convinced myself that a GPS would allow me to discover pristine wilderness locations with ideal rf propagation characteristics.

So in spite of the fact that a compass and paper maps had served me well in decades of cycling, hiking, and canoeing, I became the proud owner of a Garmin Etrex Legend GPS about one year ago.

Fig. 1 – Whether your Radio Adventure Trek is by foot, by canoe, or by bicycle, it will be even more interesting with a GPS receiver along for the ride.

GPS receivers come with a wide range of features and prices. Comparison of the units in the Garmin Product line will give you an idea of the varied capabilities. (Garmin, of course, is only one manufacturer, so take your time and do the research to decide which will GPS will best meet your needs.)

This article is not intended to be a “shoppers guide” to GPS receivers, or a detailed “user’s manual” of GPS features. Like so many other technical toys these days, a wealth of free-for-the-browsing information is available on the web. Here are just a few for your reference:

What I’d like to focus on specifically is how a GPS receiver can enhance your adventure radio expeditions.

First, a few basics ...
If you have never used a “GPS” (or if you are trying to explain to your YL why you desperately need to purchase one) the following is a thumbnail summary of everything you need to know: a GPS receiver is capable of pinpointing your precise location on the planet at any time, allowing you to find your way to important “waypoints” (e.g. where you left your car) and to keep breadcrumb “tracklogs” of your travels.

There are a number of different coordinate systems which you will likely encounter in using your GPS. Most common , of course, is “latitude and longitude”. If you already make use of topographic maps on your wilderness adventures, you will also be familiar with the useful UTM (“Universal Transverse Mercator”) system. Most GPS receivers are capable of displaying your position in either format. For vhf roving and mountain-topping, the Etrex Legend even displays maidenhead coordinates!

The most basic GPS receivers display only waypoints and tracks. More expensive units, such as the Etrex Legend, provide a “basemap” and on-board memory to accept optional street or topographic maps with even more detail. Of course, these optional maps are generally not compatible with other manufacturer’s units, and detailed uploadable maps are not available for all areas of North America.

So what can you do if the needed commercial digital topo maps are not available for your GPS, or if your GPS does not even display maps? Not a problem. A variety of exiting free “GPS interface” programs are available. My personal favorite is “GPS Trackmaker”, a versatile tool for merging your GPS data with any digital image (most commonly a scanned map). The pirate treasure map you found in your attic can be scanned and loaded into GPS Trackmaker, allowing you to define important waypoints and routes for uploading to your GPS receiver. Even easier is copying a map image from your computer clipboard into a GPS Trackmaker file.

Our U.S. friends are lucky to have gratis on-line access to topographic maps via “Topozone”. In other areas of the world, we have to work a little harder (and pay a little more) to acquire digital topographic images. Canadian Topographic maps are available from SoftMap (I have purchased sets of 1:50,000 topographic CD’s for several regions in of Ontario, and have been quite pleased with them.

To accurately paste a digital map image into GPS Trackmaker, the coordinates of two points on the image are needed (preferably, one point at or near the upper left corner and the other at or near the lower right corner). Map images to be used in programs such as GPS Trackmaker must have meridians and parallels which are of equal distance, parallel and relatively rectilinear. In other words, a section of a topographic map will work fine, while a satellite photo or “world atlas” map will not.

A series of images (such as tiled topo maps copied to your clipboard from Topozone) can be saved in GPS Trackmaker. A handy Topozone feature is the small “X” at the center of the image, for which accurate coordinates are listed at the top of the page. Fig 2 illustrates how this information can be used for accurate location of your digital image within GPS Trackmaker.

Fig. 2 - Using known coordinates of recognizable points to position maps in GPS Trackmaker

First, we obtain an image centered on our ultimate destination (Image 1 in our example). This image is pasted into GPS Trackmaker (no need to worry at this point whether the map is located in the right place!). Next, the coodinates for two recognizable points on the first image are obtained. In Topozone, you would simply click on the map to “recenter” at the chosen point, and jot down the coordinates. We’ve chosen the tip of a peninsula and a road intersection as our two points (the center points in Image 2 and Image 3). We can now go back into GPS Trackmaker and “reposition” the map image using the coordinates for the two known points. The downloadable “help” file for GPS Trackmaker will fill you in on all the details for modifying the map image properties. Of course, you can repeat the process to tile multiple images into your GPS Trackmaker file. Three or four tiled images will likely be enough to give you a sufficiently-detailed map for your whole weekend trek. As illustrated in Fig. 3, it is easy to verify that your imported map image is correctly aligned and scaled, by comparing the alignment of UTM gridlines on the image with those in the master GPS Trackmaker screen. Glaring discontinuities in elevation curves where tiled topographic images overlap is also a “flag” that an image has been incorrectly positioned.

Fig . 3 - Image UTM Grid (pale blue lines) lines up with GPS Trackmaker UTM Grid (dotted black lines). The jagged red line is a “tracklog” downloaded from the GPS, while the bright blue dots are saved “waypoints”

With the image now correctly scaled and aligned, we can use it to define waypoints, tracks and routes for our upcoming trek. Creating a tracklog to follow (for example, marking the easiest and most gradual ascent to a targetted high-point) is as easy as clicking and dragging with your mouse on the GPS Trackmaker map display, and uploading to your GPS receiver.

Note that the full detail of your map is not transferred to your GPS. That would be nice to have, but is really not required. With accurately defined waypoints (such as your final destination or the access point to a portage) and planned tracklogs loaded in the GPS, along with a weather-protected paper copy of the detailed map, your trek will be safe and enjoyable. (And please remember, do not set out without spare batteries for your GPS, and a backup compass in case the GPS fails. Dead batteries in your trail-friendly transceiver can be a disappointment, but navigating blindly in the wilderness can be fatal !)

Working with your GPS receiver and GPS Trackmaker is a “two way street”, allowing you to log and share your past adventures (by downloading from your GPS) or helping you to plan new conquests (by uploading waypoints, tracks, and routes to your GPS from GPS Trackmaker). Fig 4 is a screen capture of a gpstm file, showing the logged route of my one-day paddle up Indian Arm, British Columbia (North America’s most southerly fjord). For Adventure Radio, such an image will make a very interesting QSL card. And while on the subject of QSL’s, be sure to mark a waypoint at your wilderness operating location, for accurate “miles per watt” bragging rights. Using the “Find /GO TO” button on the Etrex Legend permits quick determination of “as the crow flies” distance to any location (city, town, or saved waypoint) in North America.

Fig. 4 - Keeping a record of your trek is easy with GPS Trackmaker. Saved tracklog is shown in yellow, Saved waypoints – including a couple of idyllic potential Flight of the Bumblebee locations- are shown in bright blue. (Original image from Deep Cove Kayak )