1.2 Field Technique Tips for Measuring %Slope

Slope generally is measured with an instrument called a clinometer. When sighting through a clinometer, the measuring line is placed on the target, and %slope is read from the scale. Both eyes are open, as one eye reads the scale, and the other eye sights on the target (Figure 1.7).


clinometer scales
Figure 1.7. A clinometer generally has two scales. In this figure, the scale on the left measures %slope. The scale on the right measures topographic slope (see Chapter 2). Also note the “plus” signs below zero on each scale, and the “minus” signs above zero on each scale. In this illustration, the %slope reading is just under 3 percent. Since the reading is on the “minus” side of zero, the person using the clinometer is looking slightly downhill.

1. Measuring %slope for profiles is easiest to do with a partner. First determine where 0 percent slope (eye level) is on your partner. Then use this point as the target when taking readings with the clinometer (Figure 1.8).   In this way, you will be measuring parallel to the slope, mirroring the land.

two people determining where 0% slope is on each other
Figure 1.8. Standing on level ground close to each other, partners first determine where 0 percent slope is on the other person. In this example, the technician on the left will sight on her partner’s nose when taking %slope readings with the clinometer.

2. To determine %slope, one partner walks up or down the slope to a point where a reading should be taken, such as a major change in slope. A reading is taken and recorded to the nearest percentage (Figure 1.9).

two people using clinometer to determine %slope on a hill
Figure 1.9. Sighting on a partner at eye level (as determined beforehand in Figure 1.8) allows a person to obtain an average %slope reading, paralleling the slope of the land.

3. When working where there is a lot of brush, it may be difficult to see your partner. A brightly colored target held at the sighting point, such as a painted piece of cardboard, can substitute for your partner. Your partner’s hard hat will work in a pinch as well.

4. When working individually on forested slopes, you will have to substitute a tree for your partner. Estimate eye level on a tree that you can see clearly, and take a reading on that point. When determining average slope on a long hillside, try to pick a point as far down or up the hill as possible, to even out the slight dips and bumps on the ground.


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Forest Measurements Copyright © 2016 by Joan DeYoung is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.