HAMAR LASER L-705, Manual

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Appendix C – Remote Buck-in
As the distance between the laser and the near target
increases with respect to the distance between the two
targets, bucking-in by the close method becomes nearly
impossible. A special remote procedure has been
developed for these situations. The remote buck-in uses
simple geometry to make the laser beam parallel to the
centerline of the two targets, and then centers the beam
on that line. Figure 26 illustrates how the remote method
works.
Unlike normal buck-in, where the laser is pointed to zero
on the far target, the remote procedure has the laser point
through zero to a point called the "set." The set distance
is the offset between the parallel laser beam and the
target centerline.
The uncorrected laser beam, the offset parallel beam and the set distance form a triangle. The uncorrected
laser beam, the target centerline and the distance between the far target center and the far reading form a
second triangle. The two triangles have the same three angles and are therefore geometrically identical
(see Figure 27).
A relationship between these two triangles can be stated in the formula, “The set is to L1 as the far
reading is to L2.” Stated mathematically, the ratio is Set/L1 = Far/L2. If L1, L2, and the far reading are
known, the set can then be determined by the following formula: Set Point = -1 * (Far reading * L1/L2).
( Note: This is a simplified formula for cases where the laser beam is centered on the near target).
In remote buck-in, point
through
zero to the Set Point. This means moving the laser until it reads the set
amount on the other side of zero from the starting point. In doing so, the sign of the number (negative or
positive) will be reversed. Figure 27 illustrates this by taking sample readings and showing how the Set
Point is derived. Notice the far reading is a negative number and the Set Point is positive as you go
"through zero," resulting in a laser beam parallel to the target centerline, but offset by the set distance.
Figure 26 –
Remote Buck-in
Figure 27 -
Calculating the Set Point