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Subject: Re: 100:1 ratio distance measurements
From: Richard M. Pisko (rmpisko1@XXX.XXX)
Date: Sat Apr 05 2003 - 03:24:08 EST
On Fri, 4 Apr 2003 17:39:07 -0800, Royer, Doug wrote:
>2.Accurate
>measurement of the distance traversed (to the inch at longer ranges) while
>moving the 10 mil angular distance is critical to keeping the measurement
>consistant.I used a tripod and a plumb connected to the Bussol and measured
>that distance from the start to the finish of the 10 mil angle.
>
I asked about the standard Soviet artillery compasses,
because I couldn't remember the figure before, and they are
generally graduated to 6,000 mils in a circle according to a
source I believe. In other words, they essentially declared
"Pi" was equal to an even "3" instead of 3.14159... the way
it really is, or 3.200 the way the US military says it is.
I have been making assumptions as to the amount of accuracy
and portability you need, which may not be warranted.
Rather than carry a tape and tripod to measure so
accurately, walk through a 100mil arc and then the object
will be away from you only ten times the distance you paced.
Alternatively, if you can keep yourself on a straight course
as on a road or with two bearing objects in line, the "broad
and beam" angles of 45 degrees and 90 degrees to the third
object with the unknown distance is probably easiest. This
is just a special case of the "double angle" problem. Walk
along a course "A-B" until the object "C" is at an angle of
45 degrees off to the right (or left) front. Start counting
the paces while still heading along course "A-B" until "C"
is off to the side at 90 degrees. Then "C" will be as far
away from you as the length of the leg you measured.
All of this should be explained with diagrams in a book of
coastal navigation, along with how to use the sextant on its
side to get the angles more accurately than possible with a
hand compass. A cheap plastic sextant is not that heavy to
carry with you while hiking, and is a lot of fun.
It does not replace a map and compass, just makes (for
example) planting and finding a cache a lot more accurate
using at least three permanent natural reference objects not
on a circle with your cache location. These can be hundreds
of yards apart.
An old survey text with references to plane tables and
mapping will make the methods more clear.
The most difficult job of locating yourself is with the
stars, sun and moon as your only guides; then you also need
accurate instruments, timepieces, and tables.
Perhaps the easiest is with a good orienteering map of the
area, with land forms such that you can recognize where you
are without even a compass.
-- Richard ...
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