🚀 go-pugleaf

You are getting into the area of remote sensing.

The principal instrument you want is Imaging Radar, also know as
side looking radar (SLAR), Synthetic Aperature Radar (SAR), etc.
(typical air or space borne).
There is also the use of passive microwave.  Radar has the
advantage in that is it an active sensor sending a pulse (chirp)
out which has a signal (return) which can then be analyzed.

IR has some advantages and disadvantages.  I won't digress.

The bottom line is that you are looking at secondary artfacts typically rather
than primary characteristics to learn about your subject
of interest.  Airborne imaging radar has been used to lcate runs in the
jungles of Central America and water ways in the Sahara (spaceborne
systems).  The mechanics of the subject are long, big, somewhat complex,
and not well understood (do you have 5 days?).  We create images, not photos
or maps, the geometry of creation is completely different from a photo (point
perspective) or a map (orthogonal).

Texts include: The Manual of Remote Sensing (Amer. Soc. of Photogrammetry),
(try 7 inches thick) and radar specifically:
Introduction to Radar Systems by Skolnick.  Lots of fun working
in this area, you get to go on field trips, take ground truth.

	"What do you do?"
	"I make maps."	-- Starman

Another gross generalization from

--eugene miya, NASA Ames Research Center, eugene@aurora.arc.nasa.gov
  resident cynic at the Rock of Ages Home for Retired Hackers:
  "You trust the `reply' command with all those different mailers out there?"
  "If my mail does not reach you, please accept my apology."
  {ncar,decwrl,hplabs,uunet}!ames!eugene
  Do you expect anything BUT generalizations on the net?