I think the processes you may be wondering about here are not thermal;
rather the "different colors" you refer to are often a convenient output
schematic for visualizing variations in forced electrical current through
the ground or relative variations in magnetic field strengths, using
resistivity detectors and magnetometers respectively.  To be sure I am no
expert in these methods, but I have used them for a similar purpose and met
with mixed results.  Their value is substantial, however, and for a good
general introduction to these methods check out a recent textbook like
Hester, Shafer, and Feder's "Field Methods in Archaeology."  The bib should
lead you from there.  Best of luck.

------------------------------------------
Michael John Madson
Graduate Student, Industrial Archaeology
Michigan Technological University
Department of Social Sciences
Houghton, MI 49931
Office Phone:  906-487-3156
Home Phone:  906-483-8267
email:  [log in to unmask]


----- Original Message -----
From: sbien
To: [log in to unmask]
Sent: Tuesday, March 20, 2001 10:26 PM
Subject: Re. techniques for locating unmarked graves


3-20-01

    I am looking for information on thermal sensing to locate unmarked
graves.  I am not exactly sure what the technique is called.  It involves
different temperatures of the soil showing up in different colors.

S. Bien
[log in to unmask]