I build alot of ground racks, but I have a painstaking unreliable means of laying them out. an example of what I build is here....
http://www.affordenergy.com/gallery/Test-Album/154_007

any proven methods of laying out perfectly square racks of varying pitches on uneven ground would be great. Thank you

The 3-4-5 Rule

For squaring use the 3-4-5 rule. The best place to start is in one corner of the layout. The corner should be a right angle with two legs (sides). The end of the left leg is A, the corner is B, and the end of the right leg is C. Tie a string between A and B to create left leg A, and tie a string between B and C to create right leg C. B is the corner.

To apply the rule, start at stake B and measure out 3 feet toward A. Mark the string. Beginning again at stake B, measure out 4 feet toward C. Mark the string. With a second pair of hands and starting at your 3-foot mark on string A, pull a tape measure to the 4-foot mark on string C. This diagonal measurement should read exactly 5 feet.

When working alone, put a stake on the outside of the string at the 3-foot mark on A and tie a string to the stake. Mark this string with a 5-foot measurement. Now, pull the string so that the 5-foot mark lands on your 4-foot mark on C.

If the distance between A and C doesn't measure 5 feet, then move A or B out or in until it does. When the measurement between the two points (A & C) reads 5 feet, your layout is square!

For larger projects simply use a larger number combination making all three numbers divisible by 3-4-5, i.e., 21-28-35 (21÷3=7, 28÷4=7, and 35÷5=7).

If you are using the frame itself, then just measure off the frame no string needed.

I use this method for cabinetry to foundations, fence lines, etc. For smaller projects I resort to using the inch marks.

I am pretty good with math, that is actually the pathagorean theorem. A squared + B squared = your hypotenuese squared. Know any two and your golden. The problem is doing it on a steep side of a hill, say a 60 x 12 rack on a big steep hump. I have done pretty well so far, you can see a few of them at http://affordenergy.com/gallery my problem is keeping everything parallel and square on any type of surface. I am considering a new laser transit. Thanks for the answer. Check out my application in the work section of that gallery and maybe you will have some furthur insight to my dilemma.
Pat

I don't know if this will help but one of the other quickies that is use in construction is to cross measure. Start at the top left corner to the bottom right. Then from the bottom left to the top right.

All things being equial, both should be the same. If not, then the frame is "Racked" and out of square. This works as long as all corners are 90 degs. whither a square or a rectangle.

By the way, if you add the two together and divide by 2, you will get the correct diagonal measurement. Then you can push or pull to that measurement and save a few steps.

ie: A 1/8 rack would be 12.375 + 12.625 = 25/2 = 12.5 for each cross section to be in square.

Minor quibble: that's the Pythagorean Theorem, named for Pythagoras. The sum of the squares of the two sides is equal to the square of the hypothenuse. The 3,4,5 ratio has the advantage of avoiding fractions or decimal fractions, or square root calculations.

Yeah the python-pylon-pygormoniaum - whatever Theory