Calculating a long right angle ?

Question

OK, this is a problem of a very practical nature:

I have an allotment which is approx 7m wide by approx 30m long but doesn't have a straight length. The width is fine as it has a path at the end so can be used as some form of reference.

I need to get as near to a perfect right angle as possible so that this and all others can be made into rectangular plots.

If this is not a good explanation, please say, so that I can elaborate.

Answer 1

egyptians used these long ago...

make a rope with 13 equally spaced knots. Tie the two ends together , connecting the first and the last knot.

from there,

make a triangle with sides 3, 4 & 5.

that will become a right triangle.. . . (pythagorean theorem guarantees us that.)

this is ... if you dont have a perpendicular square.

Answer 2

sorry, how about if you try to sketch it.

i don't not understand

thx.