To judge the grade of a hill I need to?

November 13, 2006 8:02 PM

I need to be able to judge by sight the grade of a hill / road / parcel and be accurate within about 1% gradient. Is there a software tool that I can make some triangles with specific grades to use on flash cards?
posted by bigmusic to science & nature (13 comments total)

I think it will be hard to get that degree of accuracy by sight. (Although you will be able to guess pretty close, especially with practice.) Is this for surveying, or for ADA compliance, or something else? Are you going to be viewing these hills in an unnatural situation -- eg a side cross-section? or will you be viewing them face-on in a natural setting?

If you only need one set of flash cards, you can construct the triangles you want most simply by using a protractor and pen. No muss, no fuss, no learning curve.
posted by LobsterMitten at 9:39 PM on November 13, 2006

I would be viewing them in thier natural setting, face on. Basically it would be for an initial assessment of land for construction. It doesn't need to be extremely accurate.

If there is a tool that I could use on site, that I am not aware of, that would be good too.
posted by bigmusic at 10:27 PM on November 13, 2006

Could you maybe use a small level and a protractor to take measurements?

Alternatively, you could just snap off a picture with a digicam, and use Photoshop (or similar program) to generate some numbers.
posted by unmake at 10:49 PM on November 13, 2006

Aha! The internet works its magic. The name of the thing you need is "clinometer". To use one you will need a distance measure to the top of the grade you're measuring, I think; check the bottom link.

- Here's a quick explanation of how to use one to measure grade up to a landscape feature.
- Here's a diagram of a homemade clinometer.
- How to use a homemade clinometer (scroll down, the clinometer info is in a gray box close to the bottom of the page)
posted by LobsterMitten at 11:54 PM on November 13, 2006

Not a distance measure; a buddy and two sticks of equal height.
posted by LobsterMitten at 12:00 AM on November 14, 2006

LobsterMitten is right. Here's a link to a catalog with clinometers
posted by X4ster at 1:23 AM on November 14, 2006

Is there a way to use a clinometer without having another person help you and without pounding a stake in the ground?
posted by bigmusic at 1:38 AM on November 14, 2006

Use a tripod set your your eyeball height + Clinometer
posted by Monday at 1:56 AM on November 14, 2006

The ultra cheap solution? A small hand level and a protractor. Place the protractor on top of the level and sight along it as close to your eye as possible. Pick the angle on the protractor that matches what you are sighting.
posted by JJ86 at 6:06 AM on November 14, 2006

Is there a software tool that I can make some triangles with specific grades to use on flash cards?

AutoCAD or something similar (Google sketchup?) would work pretty well. Draw a 100' long horizontal line, then a vertical line at one end of that line equal to the height of whatever grade you want. These would form two legs of a right triangle, with the hypoteneuse being the actual slope.

As for measuring in the field, get a yardstick and a five foot stick with a level on it. Set on end of the yardstick on the ground, and set up the five foot stick so that one end is touching the ground and one is touching the yardstick. Adjust the five foot stick until level, and check where it ends up on the yardstick, which will be how much elevation gain you have in a five foot run. Multiply that measurement by 20 (after converting it to feet) and you've got your percent slope. So, a three inch gain over five feet would equate to a 5% slope (.25' x 20).

Most manufactured grades won't ever be greater than 50%, while streets generally won't be more than 15% although they used to make them much steeper--some streets in my neighborhood approach 28%. In my area, driveways can go up to 20%.
posted by LionIndex at 7:57 AM on November 14, 2006

Note that using a protractor to get the degree of the slope will require you to do some trig to get to the actual percentage slope.
posted by LionIndex at 7:59 AM on November 14, 2006

How about a $25 inclinometer designed for mounting on bicycle handlebars? Rig up some mounting system, measure away.
posted by fixedgear at 8:40 AM on November 14, 2006

subsequent similar question, for extra reference.
posted by LobsterMitten at 10:27 PM on April 25, 2007