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msar-riders - Re: [MSAR] Compass or GPS?

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  • From: Una Smith <una.smith@att.net>
  • To: Mounted search and rescue <msar-riders@lists.ibiblio.org>
  • Subject: Re: [MSAR] Compass or GPS?
  • Date: Sun, 24 Jan 2010 09:16:53 -0700

On Sat, Jan 23, 2010 at 10:04:23PM -0800, Philip & Bonnie Easley wrote:
>With the GPS working, I cannot see how a compass can compare.

I use both GPS and compass. There is surprisingly little overlap in
their uses. A GPS with an actual compass on board comes pretty close
to doing what a good baseplate compass does, but for work with a map
and for taking bearings I still prefer an actual compass.

To use a GPS with a map it helps enormously to draw the UTM grid on
the map. Many maps now come with the grid pre-printed. Doing it by
hand takes a flat place to work (side of my trailer), a long straight
edge, and about 5 minutes per map. I usually fold my map to hold in
one hand, inside a plastic bag, so to use GPS and map I also find it
necessary to write grid numbers in each UTM km square along my route,
so I don't have to keep unfolding the map to read its margins.

I use the GPS to record my track, to monitor my rate of travel, to
give a fast and reasonably accurate estimate of when I will reach my
next waypoint, and to quickly get my UTM coordinates for calling in
over the radio.

I use the compass to orient myself and my map to the terrain, and to
take bearings on visible landmarks to determine my exact location on
a map that lacks a UTM grid. I also use it to "map" fences and other
linear features in the landscape, and take bearings to sounds heard
in the forest. Triangulation of gunshots and other distress signals
detected at long distance can be an important skill for searchers.

In much of the United States, in so-called "Township and Range lands"
maps are marked in square miles called sections, and roads and fences
run on section lines. In those areas it is common for searchers to
give their location as the section they are in, and if relevant which
quarter. Standard USGS 7.5 minute topo maps print the section number
in the center of each section.

Una Smith
New Mexico




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