Laser Setup
Topcon AG System Five Operator’s Manual
3-14
Setting Grade Reference Points
Recognizing and measuring errors help to minimize problems and
maintain productivity. Once errors are identified, they can be
measured against pre-set benchmark hubs or finish grade spots.
These grade control reference points can be used throughout the job
to verify grade. Set up at least four reference points, one on each
axis. On larger projects, use eight benchmarks, two on each axis.
When setting up control points, place the benchmarks 800–1000
feet/305 meters from the transmitter, or near the ends of the field for
small projects (Figure 3-12).
Figure 3-12. Set Grade References
If you suspect laser drift, atmospheric bending, or some other
problem, use a grade rod on the benchmark hubs, or the implement
on the finish grade spots, to measure the error. In most cases and
with little or no drift, you can compensate for the small changes that
occur from atmospheric bending.
• For 500’/152m to 700’/213m from the laser, there will be little
change in grade.
• For 1000’/305m or more, elevation changes will be consistent
for a given distance from the transmitter.
Use Grade Rod &
Detector To Set
Reference Hubs
OR Cut a Small Area to
Finish Grade to Use as
Reference
Set Additional
Hubs For
Large Prjects
800' to 1000'
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