I am trying to find information about the location of reference rod placement for measuring ground resistance using the fall of potential method. Someone mentioned IEEE 81, but I do not have a copy. Does it has procedures for doing the emasurment, like NETA has for breaker and cable testing etc.

It appears there are no standards.

According to a technical bulletin I have from AEMC Instruments:

{First some terms, for Fall Of Potential ground resistance testing, three points are used: X is the ground electrode under test; Y is the auxiliary potential electrode (sometimes called P); and Z is the auxiliary current electrode (P).}

"The goal in precisely measuring the reistance to ground is to place the ...Z electrode far enough from the ground electrode under test so that ... Y will be outside of the effective resistance areas... The best way to find out... is to move [Y] ... and take a reading at each location... The readings taken should be relatively close to each other..."
"No definite distance between X and Y can be given, since this distance is relative to [many factors]..."

IEEE 81 IS the standard, in the US anyway, but it covers a lot of territory.

You might like to follow some of the links posted in this thread as well.