Transit On Slopes

bradjacob

I know the method of laying out a building with a transit. Plumb over point, shoot the other reference point, then swing a 90, repeat, etc... Pathag-theory. But this seems to only work with level grades. What happens when laying out a building and ground slopes, and slopes a lot. Does this method still work? Any good online reads on this very topic - OR - does someone care to explain it to me?

Thanks.

cexcavation

Pythagorean still works on slopes........the trick is that your slope is is the hypotenuse. Use your transit/laser to figure out your height difference, plug in your required footprint dimension, and that will give you the distance needed along the slope/hypotenuse. Across the slope would not apply since the plane of reference is the same as normal. As I write this it is becoming apparent that I need a stick and a nice patch of sand to draw this out. Point being, if you understand the pythagorean theorem, then you will be able to manipulate it to figure out your footprint on the slope. Good luck

bradjacob

Yeah, I think I got it. On a flat plane, the hypot would be the transit's line of sight to the tape measure. On a slope, the transit's "level" line of sight would be the "straight" part of the right-triangle and the down-slope would be the hypot.

Any insight on what you would do id the ground went up, then down, then up, then down (you get the picture) - really uneven and all over the place...?

tgeb

What is the difference in elevation total?

I'll use a plumb bob or an eight foot level to drop the point down to grade.

If it gets to be too much....the heck with it, let the builder hire a surveyor to do the layout.

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www.gebcon.com

cexcavation

"Bumpy Ground" definately poses a problem. My method works well from an excavator's standpoint since I will over dig, get flat and then nail everything down precisely with the newly prepared surface. If you are trying to build on the existing surface, then TGEB's method would work better. Another trick would be to go oldschool with batter boards, a string level, plumb bob, and tape. Point being, uneven terrain posess challenges to getting your footprint dead on without any surface prep. If the ground isn't too "bumpy", You can pull everything up say 1' to clear all obstructions, subtract that foot from your original height difference. Using stakes and a plumb bob for a one foot drop would be darn close if not right on. I am sure I just made it more confusing, but let me know if you want me to try and clear up my thought process

bradjacob

Nope - actually you made it crystal clear. You clarified what I already was thinking, so I'm happy that I was on track. I thought about my question (crazy-bumpy, uneven grade) and it made sense that when laying out a large building, I'm sure that the excavators will prep the ground and make the surface pretty flat - or at least smooth, so the grade drop (or rise) will be smooth and flowing.

Thanks (everyone) for you help.

neolitic

You might be interested in this.
http://www.ce.memphis.edu/1101/notes...g_distance.pdf -

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