Sorry Guys; sometimes i can be pretty dense; but I have quite a few hills I'd like to figure the degree of slope of (for point of reference). I understand the formula ( i think) but how in the world can i measure the distance up or the distance forward. Is it just a two person opertation holding a tape as steady as you can at some point in the air and measuring forward and down?
moon..
If you do this, you need a clip on level to ensure your horizontal is level.
So:
Use the same length for horizontal to simplify your calculations...remember the level!! I suggest you use 100". I also suggest you use a straight edge or cut the straightest 2"x4" you can find to a 100" length.
Set your horizontal (level), then measure down (tape measure is fine).
Record the "down" (better expressed as VERTICAL) dimension.
Divide the VERTICAL dimension by the HORIZONTAL dimension. If you're using a CONSTANT HORIZONTAL (as suggested above), this will be easy.
This will be the tangent of the angle. Either look up the angle in the Trig charts (if you have them) or, if you have a scientific calculator, use Inverse tangent. The TANGENT will be the percent slope (remember, the tangent of 45° is 1.00 (or 100%). All tangents > 1 multipled by 100 would give you the slope percent. The INVERSE TANGENT would give you the slope in degrees.
Do this at least 3 places on a slope (try to stay on one path going down the slope), then average that number..better if you do it 5 places..but 3 should give you a good average.
Example:
26" VERTICAL divided by 100" HORIZONTAL = .26
.26 times 100 = 26% slope
INV. TAN of .26 = 14.57° slope.
The easier method would be to buy a gauge designed to measure slopes (angles). These are available (I had one I got thru Sharper Image years ago...but it broke).
I'm sure these would be available at hardware stores. If you use the electronic gauge, I suggest you mount it on a straight edge of at least 72" (6'), and again, check the slope at least 3 places and average those measurements.
Now, I have to thank several folks who squared me away on the definition of percent of slope. That was the hard part...
If any of y'all disagree with the methodology..no prob..but have your math ready.