Spectra Precision DG613, Information Manual

Page: 9 / 37

Example 1: Setting the Grade Rod on top of the Top Pole Scale
Step Description Feet / Inch Metric
Step 1
Decide what elevation the laser beam shall be
used above the invert.
0.5 ft 0.152 m
Step 2
Record the “Cut to Invert” information from
the grade hub.
2.64 ft 0.805 m
Step 3
Measure the elevation (HI) of the optical
instrument above the grade hub.
3.70 ft 1.128 m
Step 4
Subtract the measured distance from the
optical instrument to the top of 1239
Universal Fixed Pole
-5.38 ft -1.635 m
Step 5
Subtract the desired elevation of the laser
beam above the pipe’s invert.
-0.50 ft -0.152 m
Step 6 Calculated TPS =
2.64 ft
3.70 ft
-5.38 ft
-0.50 ft
0.46 ft 0.805 m
1.128 m
-1.635 m
-0.152 m
0.146 m
Step 7
Adjust the pole clamp until the reading edge is aligned with the TPS
reading (0.46 ft or 0.146 m)
Step 8
The laser beam is now set at your desired working elevation (6 inches /
0.5 ft / 152.4 mm) above the invert of the proposed pipe.