Whats wrong with ' overlapping resistance areas ' ?

John Rumm wrote:
"Multiple rods are ok (and are commonly used in the supply side of PME
installations for example), but ideally don't want to be too close
together such that they are in overlapping resistance areas. "

The existing earth rods are about a yard outside the backdoor,
the proposed indoors one would be just inside the back door under the consumer units.

The existing TT earth inductance was measured a new weeks ago and was OK,
but I dont have the figures here.

[geoorge]