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Topic: geophysics (Read 3 times) previous topic - next topic

wwbrown

The accuracy usually stated in the GOS specs are the horizontal uncertainties, the vertical uncertainties are much higher.  You can get sub-meter vertical accuracy with additional GPS units and some pretty intense processing, but not with a signal GPS receiver.

tjfinan

This type of surveying does not require vertical accuracy. The 2d data can be easily draped over a typical topo survey.

The point is, though, that this kind of survey could also be set up to take interval readings for a grid without gps. We don't need to get bogged down with gps accuracy.


Chuck_Young

I too love to make geophysics equipment.  I hate to rain on your parade, but those of you
thinking of making a resistivity meter should search online for DY4300. You will find
a Chinese earth resistivity tester selling for about US$ 240 including shipping.
I have one and I like it.  For it to act like a geophysics resistivity meter, you operate it in
4-terminal mode, or "rho" mode. In "rho" mode, you enter the Wenner electrode spacing and it
computes apparent resistivity.  It stores the  data internally (for about 1000 readings), but
it does not transfer the data to a computer (oops).  You have to do that manually.
A person might contemplate getting under the hood and finding a way to extract the readings
electronically. Maybe in five years a new model will come out that will allow the readings to be downloaded.

I think the Arduino is good for making other geophysical equipment, for
example a two channel VLF receiver that would emulate a Geonics EM16 or
ABEM WADI. Our efforts might better be spent there.

Chuck

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