Almost everyone wants to know how long a trail is before they hike it, or how far it was that they actually hiked. Calculating the actual distance covered by a trail is far from an exact science, though, unless surveying tools are used.

To determine the trail distances I indicate in my trail descriptions, I've used any of six different methods. Which is most accurate? It's hard to say--they all have their faults, though GPS is probably the leader. Here's a brief description of each, with what I see as the good and bad points that they have.

Dead Reckoning.

This is simply counting the number of steps you have taken to go from one point to another. If you know the length of your stride, you divide the number of steps by your stride to get the actual distance traveled.
Pros: You are actually in the field doing the measurement, taking every step. The US military (including such elite units as the Special Forces, or Green Berets) have used this method quite successfully to place themselves at desired locations. When properly done on fairly even terrain, this should be one of the most accurate methods.
Cons: You have to accurately keep count of the number of steps; you have to measure your stride carefully; it is very difficult on rough terrain to maintain a consistent stride.

Pedometers.

Actually, a pedometer is the same as dead reckoning, except you've got a mechanical device that keeps count of the steps and does the calculations for you.
Pros: Same as dead reckoning with the added benefit that it can keep a more accurate count of the steps.
Cons: Same as dead reckoning, with the added problem that incorrect placement of the pedometer on the body may make it miscount.

Trail signs and experienced hikers.

This is pretty self-explanatory.
Pros: Enough people with enough experience and using any or all of the other techniques I mention here, as well as others, have pretty much worked out the distance.
Cons: Don't believe everything you see or hear! I've seen trail signs within a few hundred yards that differed by miles. Someone very familiar with a trail may have mislearned the distance and doesn't even think about it anymore.

Map measurements.

There are several different techniques and devices used for measuring distances on a map.
Pros: You've got everything you need right there to do the measurement; it's faster and easier than getting onto the trail so you're less likely to make an error in any step or calculation. On rougher terrain and over longer distances, this should be quite accurate.
Cons: No matter how careful you are, you may miss a turn, shift a little as you measure, or otherwise blow it; errors tend to be cumulative --though they may cancel each other out, too; the trail may be mismarked on the map; it doesn't take into consideration the contours of the land, only pure horizontal distance; measuring devices may not be able to handle the fine turns of a trail, especially where there are switchbacks.

Computerized maps.

A number of companies have maps on CDROM or online. TOPO!(R) is one company that has USGS topographic maps of various areas of the country. They include many useful features, including trail measuring tools.
Pros: Extremely easy, reducing the tediousness of manual map measurement with its myriad errors; extremely fast; includes vertical as well as horizontal travel for a (theoretically) more accurate result than plain map measurements.
Cons: May not measure in small enough increments to accurately track a trail with frequent turns, as through switchbacks; the accuracy of some products may be questionable. I have used the TOPO!(R) product for certain trails in Yosemite National Park and found that it always calculates a distance less than any of the other methods, in some cases by 25% or more. I have not done a scientific comparison with ground measurements of confirmed distances, so it's conceivable that TOPO!(R) is correct.

GPS (Global Position Satellite) systems.

Perhaps the best of the simple ground-based methods.  Using satellites to pinpoint your location as frequently as several times a second, your exact position can be plotted, measured and saved. With appropriate software, you can overlay your traveled trail onto maps and mark key points. Garmin (R) and Magellan (R) are two companies that make and sell GPS units. Even with their faults, I usually would consider a GPS the best way to measure distances in rough terrain.
Pros: Extremely easy to use once you understand the basics, though you need to actually travel the route to get the benefits of true distance traveled.  You can also download routes to a GPS unit which will then point out the proper direction to you.
Cons: Needs batteries, which can die at inopportune times, can get confused by broad expanses of rock, ice or other flat surfaces, or even by mountainous terrain, has to have a good view of enough satellites before an accurate reading can be made, under some conditions they can be inaccurate by more than 75 yards per reading, sometimes they will not read accurately when in a pocket or pack.

Return to Wayne Brink's Esoterica

Last update and copyright © 05/24/2006 by Wayne Brink, email: wbrink@qcc.mass.edu

Visitors since 7 April 2005.