I often think back to when I first started hiking in Virginia the winter of 1992-93. Three of my now "critical" hiking accessories really did not exist. Back then, nobody used hiking sticks - something I consider critical to my hikes today. I remember one fellow on the PATC trips having a cell phone that came in a small suitcase. Otherwise, nothing. And GPS receivers did not become common until after the Clinton administration declassified use of the U.S. satellites allowing for such use. This occurred ten years ago on May 1st. Being an arrogant map guy myself, I didn't bother purchasing a GPS until 2007. I bought a handheld GPS then to introduce Will to geocaching and try to get him more enthusiastic about traipsing through the woods.

The "GPS vs. compass" debate is always kind of humorous, with self-righteous old school outdoorsmen expressing horror that the GPS might somehow replace map and compass. I don't see it happening. But I also would never go on a hike without my GPS. I say that not because I depend on it to tell me where to go, but because it records where I have been. At the end of my hike, I have a record of each minute of the hike, the exact location, the distance traveled (by minute) and the elevation at each data point. This is what allows me to state distance, elevation gains and difficulty of each hike. And I can put this data onto Google Earth and see a representation of where I went from the sky.

Difficulty is computed using something I call the "PATC Difficulty Factor." This is a calculation I first saw on hikes reported in the Potomac Appalachian Trail's newsletter. It is the square root of ((2 x elevation change) x distance). The final number is the square root of the sum of those numbers.

This number isn't perfect. It doesn't, for example, differentiate between two relatively flat trails where one is on dirt and the other is over a rock field. Traversing over rocks that sometimes move and constantly threaten a twisted ankle is much tougher than an equally long and flat section of trail over dirt. But it provides a start.

I use a Garmin 60CSx. Not sure it is what I would buy today, but it has provided me with great reliability for the past three years. Garmin charges extra for such seemingly basic items as detailed maps and topographic data. I have never been willing to fork over the extra $100 for this software because, as I have said, I use the GPS to record my movements, not direct me where to go. But it also means that only main routes like interstates and U.S. Highways show up on the screen.

Garmin is also not real good with the owner's manual information. I have figured out a lot of what I do through trial-and-error. Even three years after owning this unit, I feel that there is a lot I could learn if someone came out with a good "idiot's guide" for the unit. Such a guide should include information on how analyze the data and would give an explanation for the parts of the unit that I never use. There is nothing like that out there. I am glad that I decided, after about 6 months of using the receiver, to save the data on each hike to a flash drive. This has allowed me to go back and work on data after I have increased my knowledge, such as analyzing my last Grand Canyon trip a year after taking the hike.

Using Wikiloc.com, I can sometimes get GPS data in advance of a trip to get a sense of what is in store for me. There aren't a lot of trails on this site, however, so it is hit and miss. And even when there is a trail loaded, sometimes the quality of the data is not that great. For example, note the statement accompanying the Half Dome ascent on the website: "Unfortunately, there is a lot of bad data from Happy Isles to the top of Nevada Fall and beyond due to surrounding terrain. You get the general idea though :)" (Note to hiker: "general idea" doesn't cut it, dude!) These hikes can be accessed through Google Earth though they aren't as fancy as the other G.E. feature for hikes, called Everytrail.

May the journey become the quest. Enjoy.

ReplyDeletemichael.

Your description of the formula for the difficulty factor is unclear. You claim it's the sum of square roots of two factors, but you neglect to mention more than a single factor. It looks like you have sqrt(2*elevation*distance), where I presume you're doing elevation in feet and distance in miles, which is a rather odd number, with units length.

ReplyDeleteDo you mean for the formula to be sqrt( 2*elevation + distance), or perhaps sqrt(2*elevation) + sqrt(distance)? Those both have units of sqrt(length), which is again rather an odd unit to describe the difficulty.

The Excel formula I use is =SQRT((2*total altitude gain in feet)*total distance in miles).

DeleteIt really is an inexact science when using consumer grade handheld GPS data, as both mileage and elevation can be considerably off of the true data. And then, when you consider that trail conditions are not factored in - a trail with soft pine needles is equal to another trail featuring loose rocks in these calculations - the entire process is really just an estimate of which route is more difficult.