Your scheme is doomed to failure.

Although signal strength is proportional to disrtance it
is also affected to too many other things as well.

For your scheme to work both transmit and receive
antennas must be truly omni-directional with no
lumps in the polar diagram (not easy espicially
mobile). The terain must not cause any disturbance
to the signal (impossible). There should be no
reflections. The transmit power or receive gain
must not change. I am sure there are a few more
that I have not thought of off the top of my head.

Having said that such a scheme could give a very
approximate location if the data was analysed and
anomolous readings ignored.

Regards
Jeff