QUESTION:
Is there any way that repeat passes from the different relative positions of
receiving dish or dishes and the lander/sojourner could act like
differential GPS in providing exact positioning of the equipment?

ANSWER from Pieter Kallemeyn on July 28, 1997:
There have been some studies done where one or two Earth stations
simultaneously receive the signal from both the lander and the rover and
provide accurate knowledge of their relative positions.  However, since the
rover does not communicate directly with Earth (its antenna is too weak)
such an experiment will have to wait until another more power rover rolls
out on Mars.

Pieter Kallemeyn, MPF navigator