How do we map a trail?

     by Darwin Poulos

The tools we use are simple: a compass and an engineer's wheel (or other measuring device). The only other skills necessary are a knowledge of topography and lots of patience. The Map Committee has used the USGS topographic maps as "base maps" onto which we plot any data gathered in the field.
     We usually work in teams of 2 or (preferably) 3. One person doing one of the following duties: (1) taking compass bearings, (2) measuring distance from point-to-point, and (3) taking notes and recording data. The procedure we use is fairly simple. The team notes their staring point on the base map (or a copy); this will "place" them in the area to be mapped. All measuring devices are set to zero and placed at the staring point for the trail to be mapped.
     The person with the compass directs the person measuring to traverse the section of trail is an approximately straight line. The note taker notes the length and compass bearing of this segment of trial. One of the most critical notes is whether compass bearings are relative to magnetic or true north. The person taking compass bearings then moves to where the measuring device rests and the process is repeated until the entire trail is mapped. Turns and bends in the trail can be approximated by a series of straight lines. The note taker should also note special features of topography that will "place" a trail segment on the base map. The amount of detail that needs to be recorded will depend upon the scale of the final map. Trail junctions should always be noted.
     How is this data used to create a map of the trail? There are several ways of plotting the data gathered in the field. All of which are different embodiments of the same principle, that is, joining vectors head-to-tail. Any spreadsheet program can easily accomplish this procedure. The resulting chain of vectors can be plotted to any given scale (by trial and error) and overlaid/traced onto the base map. Several of out volunteers have written computer programs to do these calculations and plot the data at any given scale.
     When the trails of interest are mapped and plotted on the base map one can start production of a "mock-up" of the final map. This mock-up will aid in layout and design decisions. The challenge of writing trail/park descriptions is always a concern. This element of the map can be critical to its success or failure.
     The final stage of volunteer work is creating the "electronic map" that a printer can use to create a printed map. There are several way of accomplishing this task. The method that the Map Committee has used is to scan the mock-up and overlay the trails from that scan onto USGS (or similar) data that include topography and other features.

Copyright © Trail Center. All rights reserved.

Please contact the Web Manager for corrections or comments.