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HOW TO SET SLOPES (FALLS/GRADES)
Working Example 2 (when you do NOT know the % grade to set)
The following description explains the general principles of setting a Slope (Fall/Grade) using
your Spectra laser, when you do NOT know the % grade to set.
Equipment
You will need the Spectra laser level, its remote control, a surveying tripod, measuring staff (rod)
with mm scale and a laser detector/receiver.
Site Conditions
There are many diff erent work site scenarios. As an example, we are assuming that you are
outside, on a site with a clear fi eld of view and planning to set drainage falls.
See Diagram 1
A is a manhole cover with surveying tripod and attached Spectra laser level.
B is a second manhole cover at a lower position, located at distance of “D” apart and by a fall of
“F”.
The planned sitework is to set a slope on the laser level to assist in digging a drainage channel to
join A to B.
Procedure
First measure distance “D”.
Next, attach the laser level on the surveying tripod, switch it ON and allow it to auto (self) level.
The tripod height is unimportant. Face keypad (Y axis) towards cover B.
Position your extended measuring staff on the ground next to the laser & clamp the detector to
pick-up the rotating beam to give a continuous tone on the detector.
Note & record the mm height from the scale on the measuring staff .
To determine & set fall F:
Before moving position from cover A, press the laser’s Manual Override button to disable the
auto (self) levelling. On the LL100N, this is only found on the remote.
Do NOT un-clamp detector. Move position and place extended measuring staff over the
centre of cover B, holding it vertically (see diagram 2). Un-clamp detector and move it up the
measuring staff to pick-up the laser beam with a continuous tone. (see diagram 3). Record the
new height value. The site Fall “F” is this value minus the value taken before at cover A.
Return the detector down to the lower position again & clamp tight. See diagram 2.
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