TEHCC Wiki:Trail Elevations
Trail Lows and Highs are as simple as it sounds. If using a GPS points or tracks, having the points locked to USGS data is preferred to remove GPS error.
Trail elevations and elevation changes is trickier than one would initially believe. All sorts of factors can affect the calculation. For a detailed explanation of this difficulty you can visit the GPS Visualizer website. This can explain in detail these problems, but suffice to say there is a compounding of GPS accuracy and deciding what constitutes an elevation gain. (is walking a trail with 100 ten foot ups-and-downs the same as walking the same distance but ending 1,000' higher?).
This website is trying to "standardize" on using the calculations available on GPS Visualizer using the recommendations with a 10m gain threshold (~32.8') and 10m trackpoint distance threshold, while locking elevation data to USGS data. This is up for discussion and will need to compare with how others "feel" the trails are in terms of elevation changes.
To determine your trail elevation information, visit this page at GPS Visualizer. You can upload a GPS track and have it calculate the min/max/gain/loss for your track as well as track distance. Obviously the gain/loss is direction important. This page will also generate a profile map that can be added to the trail page as well.
Of all of the options, only a few are required for the desired output.
- Change Units to "U.S." - Note! inputs are still in meters
- Change "Add DEM elevation data" to "USGS NED1 (30m res., North America)"
- Change "Calculate elevation gain" to "Yes"
- Add "Elev. gain threshold" of "10" - meters
- Expand Advanced Options for Track/line options
- Add "Trackpoint distance threshold" of "10" - meters
- Find your GPS track data
- Select "Draw the Profile"
- Collect the information and save the profile picture for adding to the trail page