T
AKING A
H
EIGHT
M
EASUREMENT
Page 31
Electronic Copy of LTI’s Impulse User’s Manual 8
th
Edition © October 1998
calculate a horizontal distance of the highest
possible accuracy.
The measuring point of the Impulse is at the center
point of the instrument. That point corresponds to
the yoke mounting point, so if you are using a tripod
or monopod, enter a pivot offset value of zero.
If you are using the instrument hand-held, the pivot
offset is of more concern. In this case, the offset
value depends upon how you hold the instrument
when you take a reading. For example, you might
hold it close to your face, or with your arm extended
out. If you hold it so the scope is against your eye
(without moving your head during a height
measurement), you will want to specify the back
panel as your pivot point. That means specifying a
pivot offset of 0.08 meters (0.25 feet).
However, if you hold the instrument close to your
eye and tilt your head during a height reading, the
pivot point should be moved from the center of the
instrument to the back of your head.
Depending upon the precision necessary for your
height measurements, you can approximate your
pivot offset value, or use the formula at the end of
this chapter to calculate an exact pivot offset.
Here’s how to set a height pivot offset:
1. Use Forward/Back as necessary to show the
SYS option indicator.
2. Press Fire to select the SYS option.
3. Press Forward repeatedly until the PIVOT
indicator in the lower left corner of the display
window begins blinking, and HT is displayed in
the top left of the
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