Locating Bedrock

[Roger]

Can anyone tell me what i need to build to locate bedrock. I would like to map the bedrock in an area of 50' by 50'. I think the bedrock depth is between 2' to 30'.

Thanks for any help i can get
Roger

[kev]

Locating Bedrock

Hi Roger,
You could use Earth Resistivity measurements to map the sub-strata, but an easier way would be to use a Magnetometer. If you look on this site on the Geophysics and the Magnetometer forums you will get more info. Carl has plans for a Fluxgate Mag on site too, and EPE Magazine has projects for both an Earth Res and the Mag, or you could build your own Proton Prec Mag.

The EPE project has free software to help interpret the data, which is the important thing. If you can write a little C, you could write a program to process the Earth Res measurements as these need to be put through a couple of functions to convert to real depth readings. The function is available in an ETI pdf in the projects section, its for an old analogue...move the stakes after each reading setup...sounds monotonous. I don't know what resolution you would get with either, it may require drilling a test hole or two to confirm the bottom isn't false.

I've often thought of using a Mag with my metal detectors when nugget hunting to find areas of shallow alluvium. I have a couple of FGM-3 sensors so will pursue it one day.
Cheers
Kev.

[J_Player]

Hi Roger,
Somebody asked that same question in the geophysics forum. Here are some more answers that may help:
http://thunting.com/geotech/forums/s...ad.php?t=13085

Best wishes,
J_P

[Roger]

Thanks kev & J_Player, Its people like you that make it a great forum.