100:1 ratio distance measurements
Subject: 100:1 ratio distance measurements
From: Royer, Doug (doug.royer@XXX.XXX)
Date: Fri Apr 04 2003 - 20:39:07 EST
After experimenting with the double angle and the 100:1(Mr. Pisko's) methods
of distance measurements using a hand held compass I have the following info
and wish to share it with those who are interested.
Double angle method:
1.I found that no matter the range to be estimated or measured a high end
compass will yield more accurate and consistant results reguardless of the
ref. distance.A compass with small degree gradiants and a good lens to read
the gradiants(clarity of the lens to distinguish the small changes is the
key I believe)is needed.With a compass that has larger gradiants and
inferior lens the measured angle is more of an approximation than a
measurement.Common sense kind of dictates the above but it was one of the
findings.
2.The closer to 45* that the outside angles approach,the more accurate the
measurements.At around 45* the overall measurements fall within + or - 6% of
the lased distance.At angles at or below 40* the measurements fall to + or -
15% or more depending on the distance of the object.
100:1 method:
1.Here again a higher end compass gives better results.I found that this is
even more important using this method.A 5 mil gradiant compass is vastly
inferior to a 2 mil compass.My Commenga has 5 mil and my Soviet Bussol has 2
mil gradiants.
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.
3.I used the 100:1 method at some extremely long ranges(1600 to 8000 yds)
and the results were consistantly less than 10% of the total.You also don't
need a calculator in this method to get the distance off.That is a big plus.
4.Because of the ranges I couldn't lase the objects so the following is what
I used to calculate the distances.Please feel free to critic my math or my
proceedure.Feedback on this is desired because if my method of calculating
the distance is wrong all of the above is wrong.Or there may be an easier
way to do this.
I used a UTM projection and 10 digit coordinates for my position and the
objects' position.I then used Pathagoris' Theorum.
Distance off in meters = square root of (greater northing coordinates -
lesser northing coordinate)squared + (greater easting coordinate - lesser
easting coordinate)squared.
UTM's are in meters.Convert to yds. Dist. in yds = (3.28 x dist. in meters)
/ 3.
