It has occurred to me as well that Ground penetrating radar might also be quite useful for locating cavities. It could also be useful in determining how much water is beginning to leak into the site. (GPR is quite neat, but depth penetration may be limited.)
I assume that it works basically the same way we used to construct terrain maps back when I was working as a geophysicist.
Basically:
1) Fly an aircraft over the survey area. You should fly a grid pattern (lines and tie lines) at roughly constant altitude.
2) Record GPS (X,Y,Z) readings, as well as readings from a laser altimeter (A).
3) Ground level = GPS(Z) - A
4) Construct image based on positioning and (3).
The same process can be performed using a radar altimeter.
A couple of complications/considerations:
1) scattering of the signal. (5000 feet may be quite high - we normally flew at 200-300 feet.)
2) roll and pitch of plane.
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It has occurred to me as well that Ground penetrating radar might also be quite useful for locating cavities. It could also be useful in determining how much water is beginning to leak into the site. (GPR is quite neat, but depth penetration may be limited.)
I assume that it works basically the same way we used to construct terrain maps back when I was working as a geophysicist. Basically: 1) Fly an aircraft over the survey area. You should fly a grid pattern (lines and tie lines) at roughly constant altitude. 2) Record GPS (X,Y,Z) readings, as well as readings from a laser altimeter (A). 3) Ground level = GPS(Z) - A 4) Construct image based on positioning and (3). The same process can be performed using a radar altimeter. A couple of complications/considerations: 1) scattering of the signal. (5000 feet may be quite high - we normally flew at 200-300 feet.) 2) roll and pitch of plane.