theory in ground rod placement is that the ground
rod should be placed at a 90 degree angle to the target
utility and as far away as possible. In the congestion
of the real world this is not usually practical. When
attaching to a ground or placing a ground spike, care
should be taken to not cross over other utilities.
If another utility becomes a return path for the current
then distorting signals may be the result, making
locating more confusing and less accurate.
you need to, you can look for other grounding opportunities.
Metal road signs or telephone pole stabilizers can
offer a good ground. (Be careful when using buried
metal fence posts as this can then illuminate the
whole fence if it too is metal and cause distortion
if you are locating nearby.)