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Homework #8: Due Saturday March 30 by 12noon.
- section 5.8.2 These are the 4 basic electrode configurations. Note that the dipole-dipole does not have to have all 4 electrodes co-linear.
- section 5.8.3 is all about the preparatory work for doing a field survey
That's all for homework #8 (yes, just two problems again).
- In class, I keep mentioning that the OhmMapper uses a dipole-dipole geometry. In this geometry, both the two current electrodes and the two voltage electrodes are separated by a distance 'a.' Then, the centers of these two electrode sets are separated by n⋅a, where 'n' is an integer (or, in my reserach, something like 1/4, 1/2 or 3/4). Derive the geometric factor K=2π[(1/AM-1/MB)-(1/AN-1/NB)]-1, showing all of your steps for the dipole-dipole array.
- You have seen how to use MagMap2000 and Res2dinv to do your first inversion of resistivity field data. time to practice what you've done so far. Here is a .stn file ("station" file; right-click and save this) where I've already corrected the OhmMapper geometry due to different tail lengths. Open this in MagMap2000; export it to Res2dinv with the heading "2009-Jul06, COBE survey Line H-H'; 5m and 10m dipoles, n_min=1.0" (don't include the quotation marks); when you export it choose 1.25 in the dropdown menu that says "smallest or unit electrode spacing"; open it in Res2dinv, and run the inversion (Inversion-->least squares inversion). Do a screen grab of the results, save that as a jpg (not .bmp), and then email that jpg to me with the filename COBE-yourname.jpg.