How do we map a trail?
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
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
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
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