Contributed by Mike Melnick
Navigating in an adventure race is probably the most important discipline in the sport. Keeping your team on track and choosing efficient routes starts and finishes with plotting the points given in the racer instructions.
Get to the Point
Consider Figure 2. For adventure races that use UTM grids (which is every one that I've ever raced) CP7 would be reported as 070650 and CP8 would be 070660. Because they are exactly one grid square apart, the distance between them is 1 km.
Figure 2. Portion of map with Checkpoints plotted.
To put it more formally, any coordinate that you receive in your racer instructions, you can dissect into an Easing and a Northing. Let's consider the coordinate 367946. Please refer to Figure 3
One of the obvious problems is that the coordinates given in an adventure race are to the nearest 100 m. That leaves an awfully large area of uncertainty. When plotting your point, pay attention to clues in the instructions, such as "parking lot" or "trail intersection". Then use the UTM coordinates given to get close and circle the likely actual location. Keep your circle wide so you don't let yourself get too much tunnel vision while looking for a point
UTMs are plotted in two different datums, North American Datum 27 (NAD27) and NAD83. It's happened where a race director recorded the UTM coordinates off of a GPS using a different datum than what was plotted on the race map. Racers then navigated to a location that was 220 m to the west and about 90 m to the north. If you're certain you're at the right location and there's no sign of the CP, hunt around a little.
Getting around a race course using only coordinates and a map is a challenge, but definitely something that's achievable. It goes without saying that getting the points on the map in the correct location is imperative. Which route looks good changes drastically depending on the start and end locations.