The most accurate way is to use method named "radiolocation". In the simplest way you may use avalanche transceivers. Check: http://caves.org.uk/radio/bookinfo_02.html m.s. 2. 6. 2014 v 23:17, McLendonJP@aol.com:
I would appreciate any suggestions regarding the best (easiest, quickest) way to locate points on the surface that directly overlie survey stations in the cave. For example, suppose we find a place in the cave with surface debris and would like to examine the surface directly above for an entrance or dig. The ideal solution would allow me to input surface survey data in the field using a laptop and would generate an azimuth and distance from the last station to the desired point. I've sometimes overlayed the cave map or lineplot onto a topo or satellite image to identify the general area, but I'm looking for a much more precise solution. Currently, I survey overland from the entrance toward the area overlaying the station I want to get above. As I get close, I temporarily rename the last surface survey station to the name of the station in the cave below. This tells Therion that I've closed a loop and it gives me the closure error in all three axes. The x and y axis tell me how close I am, and I can guesstimate an approximate azimuth for the next shot to get closer. This eventually gets me close, but it is subject to blunders and overly time consuming. Is there a better way, perhaps through some function of Therion with which I am unfamiliar? Thanks for any ideas.