Practical GPS
Special to The ARS Sojourner
Using a topo map, you've picked out an operating location that should give you enhanced propagation to the east and northeast. Located on the east edge of a high, forested plateau, somewhere in the American Southwest, it also looks like a spectacular place to camp. Because the nearest roads approach no closer than seven or eight miles, you plan to hike cross-country to the rim the day before the contest and camp. After the contest ends in the afternoon, you intend to hike to your vehicle, which you should be able to reach before dark, then drive home.
Dense pine-fir-spruce forest covers the plateau, so you know there'll be few landmarks. Though you do know the location of your Bee site, you don't know exactly where you'll start the hike. Using conventional methods of land navigation, you could estimate your starting point, then use map and compass to plot a course to the Bee site. Because of the uncertainty of your route, you would have to aim to one side of your destination, in order to know which way to turn at the rim. Of course, you'd have to allow extra time; and there's another catch. There's little surface water on the porous limestone plateau, despite the lush alpine forest. You would like to find at least one of several springs that are marked on your map, so you won't have to carry water for a dry camp. Using GPS, you can determine the precise location of your truck, and hike directly to your Bee site, via the three springs.
Planning
Before setting out, we need to enter several locations from the map into the GPS receiver. First, set the GPS receiver to the map datum. If you use the wrong datum, your navigation will have serious errors. The North American Datum of 1927 (NAD27) is the basis for most US Geological Survey maps. You'll find this information on the lower left corner of the map. Newer maps use WGS84; if the map does not specify the datum, use WGS84. Also, set the receiver to use miles for distance and true north degrees for bearings.
If using the UTM system with paper maps, you may want to draw 1000-meter grids on your map before leaving home. Although not essential, adding grid lines makes plotting positions in the field easier. All you need is a simple grid reader.
The approach to the plateau starts on a major highway then uses a forest road. This turnoff may or may not be well marked. At home, mark the location of the turnoff on your topo map. In order of increasing accuracy, use the eyeball method, a grid reader, or mapping software to get the coordinates of the Bee site. Enter the location into your receiver as a waypoint named "TURN".
Next, create a waypoint named "BEE" to mark the location of your operating site on the rim. Your topo map shows several springs, which may or may not be flowing. Depending on where you end up parking your vehicle, you will probably pass near one or more springs. Create a waypoint for each spring. We'll call them SPRINGA, SPRINGB, and SPRINGC.
If you have computer-based mapping software, you can create waypoints on the screen by pointing and clicking. Then you can download the waypoints to your GPS receiver using a cable. This method is much faster and less error prone than manual entry. If your compass can be set for declination, make the adjustment before leaving on the trip.
Hiking to the Bee Site
As you approach within several miles of the forest road turnoff, turn on the GPS receiver. Once it has a good fix, set up a GOTO route to TURN. This creates a route from your present position to TURN. The GPS navigation display shows the distance and direction to TURN, as well as your speed, present heading, and the estimated time of arrival (ETA). Your heading should be close to the bearing of TURN, unless you've already passed it. By glancing at the receiver, you can see when you're approaching the turnoff, without having to drive along slowly looking for it. (It's safest to have a passenger do the actual navigating while you do the driving.)
After making the turn onto the forest road, set up the receiver to GOTO the BEE waypoint. Now, as you drive south along the forest road, you can see the direction and distance to BEE. You know that BEE lies east of the road. Near your closest approach to BEE, you find a side road and turn onto it. The road wanders around on the densely forested plateau, avoiding small canyons, but the GPS display constantly shows the direction and distance to BEE. Most receivers have a moving map display that shows your position relation to your destination and other waypoints, which is especially useful as the road twists and turns. At any rate, after exploring several side roads, you get within seven miles of BEE, which appears to be the best you can do by vehicle.
Now, save the position of your truck as a waypoint. Save the waypoint as "TRUCK". Since your plan is to hike from your vehicle to BEE via the springs, you next want to create a route in your GPS receiver from TRUCK to SPRINGA, SPRINGB, SPRINGC, and ending at BEE
Before setting out, check that the route makes sense, especially the location of the TRUCK waypoint. You'll need TRUCK to find your vehicle in the thick forest on your return.
Use your compass to set out on the bearing that the GPS receiver shows for your route from TRUCK to SPRINGA. Turn the GPS receiver off after getting the compass bearing. Don't be tempted to walk with your GPS on. First, it's hard on batteries, and second, you need to watch where you put your feet while moving. Although the GPS display shows your heading and speed as you move, it's not accurate at speeds below 10 miles per hour. If you can walk faster than 10 mph, more power to you!
Instead, turn the receiver on at each rest stop, or whenever you feel the need to update your position. In this situation in dense forest, I might carry the unit in a belt pack or in a pocket so I can get it without taking my pack off. Twelve channel units get a lock and display your position within 15 seconds or so if used recently, so you can pause and quickly get a reading whenever you want.
Don't worry about wandering slightly off course. You'll have to avoid obstacles such as downed logs anyway. Each time you turn on the unit, it shows not only your present position, but also the distance and bearing to SPRINGA. The moving map page also shows your location and a line representing the direct course from TRUCK to SPRINGA, so you can see how far off course you are. Use your compass as needed to check that you're walking in the right direction. Also, at each stop, save your present position as a waypoint. Most GPS units can automatically name a waypoint for you, using a sequence such as 001, 002, 003, etc. Use automatic naming to save time, and don't bother to plot these waypoints on the map. I usually plot waypoints for important landmarks such as springs and trail junctions, but not waypoints taken at rest stops. You can use this list of automatic waypoints to retrace your route if necessary.
When the GPS unit shows that you are within 0.5 miles of SPRINGA, leave the unit on as you search for the spring. Remember that civilian GPS is limited to 330 feet accuracy, so the unit probably won't take you right to the spring. I generally zigzag a bit to scan the general area, and look closely at the map for clues to the exact location. For example, springs are often located in drainages or low spots. There may also be water tanks or other improvements. In this case, you find a dry watering trough, but no sign of any water, so you mark the spring as dry on your map.
After a rest stop, continue to SPRINGB. The GPS receiver knows you've arrived at SPRINGA, so it automatically starts navigating to SPRINGB, the next waypoint. When you arrive, a brief search locates the spring, which has a good flow of water. After filling your containers and adding iodine tablets to purify the water, you check the active route display on your receiver, which shows the distance to each remaining waypoint. SPRINGC is off to the south and not on the direct route to BEE. Because it's getting late in the day, you decide to head directly to BEE. You would like to know if there's water at SPRINGC, so you decide to check it out on the way back.
On the active waypoint screen, delete SPRINGC. Now the GPS receiver will navigate directly from SPRINGB to BEE. As you continue toward the rim, you run across a flowing spring that's not shown on your map. Because this water source is close to the rim, it'll be a good water source for your next Bumblebee expedition to this site. You save the location as a waypoint named NEWSPR, and mark it on your map. A half-hour later, you reach the rim. The view of the sandstone desert to the east is every bit as stunning as you hoped, and the promontory that you marked as BEE lies a few yards south. It turns out to be a good campsite, and the cliffs below should make for enhanced propagation to the northeast. You set your antenna and make camp.
Next afternoon, after Flight of the Bumblebees is over (a blast as usual) you pack up and plan your walk back to the truck. You could reverse the GPS route you used on the way in, but since you don't need to go past SPRINGB or SPRINGA, you create a new route, using BEE, SPRINGC, and TRUCK. That way you can check out SPRINGC on the return. After a while, you reach the SPRINGC waypoint, and after a brief search, you find the flowing spring in a shallow ravine. Now, you note the bearing to TRUCK and again use your compass to head in the correct direction.
Suddenly, you run into an old fire scar. The burn is choked with brush and downed trees, so you decide to go around it. When you reach the north side of the old burn, you turn on the GPS receiver and save your position as a waypoint, BURN. On the moving map display, the best route for your next hike to the Bee site is TRUCK to BURN, then to NEWSPR and on to BEE. You make a few notes on the map, then create a new route from BURN to TRUCK, and make it the active route. Now the navigation display shows you the distance and bearing from your present position to TRUCK. You take another compass bearing, then continue. When the receiver shows that you are within 0.5 mile of your vehicle, you leave the unit on. At 0.1 miles you spot the truck through the trees, off to the left. You've reached it with nearly an hour of daylight to spare.
On the drive to the highway, you mark each fork in the road as a waypoint, all the way to the highway. You also write the name of each waypoint on the map. When you return, you'll be able to set up a GPS route that will take you right to TRUCK.
At home, you download all the waypoints from your GPS receiver to your computer, and save them in a file called "GpsRimBee". Next time you want to go to BEE, you can create the routes in the mapping software, print out a map with the waypoints and routes marked, and upload the waypoints and routes directly to your receiver.
Although you certainly can do a hike like this with map and compass, GPS makes it easier, safer, and less time consuming.
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Bruce Grubbs, N7CEE, has been active in QRP for the last fifteen years, and enjoys
homebrewing, kit building, and field contesting. His favorite wilderness activity is exploring the Grand Canyon on trips of a week or more, and he also enjoys long backpack trips in the mountains of the west.