| Laser
Rangefinder Calibration |
Edward
Frank |
| Dec
15, 2005 18:37 PST |
Will,
Bob, Jess, ENTS
In Will's Tree Measuring Guidelines he talks about calibrating
the
laser rangefinder - essentially determining the true distances
at
various clickover points. It would be useful to expand upon the
discussion, including definitions of click-over, the differences
between
Accuracy and Precision, especially for newer members considering
buying
laser rangefinders. The explanation is excellent, but I would
like to
post something to the website dealing with just this aspect of
calibration to go with the clinometer calibration post I sent in
September. Including just this explanation as a stand alone
excerpt is
another option.
Will Wrote:
General questions
· The laser only reads in .5 to 1 yard (or meter) increments,
how can it
be so accurate?
Before you use a new laser, it must be calibrated. To do this,
stretch
out a long measuring tape flat on the ground. Have an assistant
stand at
various locations on the tape with a reflective target. Place
yourself
in a position so the eyepiece of the laser is over the “0”
mark on the
tape. Alternately, you can do this by yourself by affixing the
“0” end
to a reflective target and walking down the tape, shooting back
at the
target and noting your position at click-over. Shoot a known
distance;
say to 40 yards (or meters). Have the assistant move the target
closer
or away from you until you get to the “click-over”, or
inflection point
of the laser for 40 yards (or meters). Note where the target is
in
relation to the tape. Do this calibration over a wide range of
distances
to see the variation and correction factor to use (if needed).
For
example, if the laser reads 40 yards at a distance of 40.6 yards
based
on the measuring tape, then you would use that figure when your
laser
gives the click-over reading for 40 yards. By calibrating your
laser,
you can actually be mere inches off in the distance measuring
part of
the tree height.
Edward Frank
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