Lava tube detection

[Ccat]

Any ideas on how to detect hazards (lava tubes, deep holes, etc.) on natural, undeveloped land prior to grubbing/grading?

How do surveyors manage to “survey” Puna property given that it is overloaded with all these unknown, natural hazards?

Can a drone “see” the lava rock terrain? Ie, ignore the vegetation?


Thanks to all who reply, in advance.

Ccat