Modern geophysical methods of mineral exploration are still too expensive for many small commercial scale placer miners, and seem to require a high level of learning and deployment.  I sometimes think / dream about a simple device that would measure just one thing - depth to bedrock.  I see some of the commercial seismic survey systems use a simple sledge hammer activator (striking plate) to send out a seismic wave which is picked up by a daisy chain of geo-phones and sent to a computer to record, analyze and display the data and images. I also see simple seismic detector devices to measure earthquakes for sale for under $500 (Infiltec / Amazon).  I would think coupling the same sledge hammer activator to a simple seismic detector designed to measure one thing (depth to bedrock) would be feasible and inexpensive.  Maybe even without a laptop / expensive software but rather a single digital output / display.   Is this only in my dreams or does a device like this exist?  I recently got a quote from Geotmetrics for an entry level seismic survey system… 25k + 5k for onsite training.  So, I dream on.  

I’ve done a bit of drilling and it’s not cheap either.  Maybe there are other ideas / methods for an inexpensive geophysical method to determine depth to bedrock.  Any suggestions?