The task is this: to relocate precisely some depth markers buried deliberately in soft bedrock in a river canyon eroded rapidly by natural processes; to then measure the depth to these markers as accurately as possible - in so doing the erosion rate of the intervening bedrock can be estimated; measurements will be taken every month over several years. The depth markers will be small cylinders (~1cm x 1mm radial), buried to depth of 5-10cm (inserted in a narrow drill hole or hammered directly). Several such markers could be placed to permit 3d orientation.

I'm guessing that some kind of inductive proximity detector might suit. Can anyone advise? I realize that this application is rather unusual for this forum.

The purpose of all this is to estimate the rate of erosion of bedrock in an unusual river in eastern Taiwan, where tectonic (earthquake) and climatic (typhoon rainfall) forces are extremely powerful. Getting data on such erosion rates is a major challenge in the field of geomorphology at the moment, and the answers to some big scientific questions hinge upon it.

 

Colin Stark:
> The task is this: to relocate precisely some depth markers buried deliberately in soft bedrock in a river canyon eroded rapidly by natural processes;
...
> I'm guessing that some kind of inductive proximity detector might suit. Can anyone advise?

I don't have a solution, but one problem you're going to have is that pretty much anything you pick is going to be affected by the nature of
the material. To what extent can you assume that it's not going to change?

(Different sensors are going to be affected to different degrees and in different ways, so you'll need to find out how each is going to be
affected and keep it in mind while choosing.)

Jiri
--
Jiri Baum <[email protected]> http://www.csse.monash.edu.au/~jirib
MAT LinuxPLC project --- http://mat.sf.net --- Machine Automation Tools