DC Resistivtiy section needs some love

[micmitch]

http://gpg.geosci.xyz/en/latest/content/DC_resistivity/index.html

General issues:

• Multiple figure labels (Looks like figure numbers were hard wired at some point)
• Inconsistencies in the when discussing the geometric factor. Define it one was in the text, but then as it is presented as the inverse of that in the figure. (http://gpg.geosci.xyz/en/latest/content/DC_resistivity/DC_measurements_and_data.html#measurements-potential-difference)

[hal98x]

I will add too this this page has some old concepts such as pseudosections. While I understand that pseudosections are an easy and effective way to present the concept of profiling, nowadays pseudosections aren't used much practically. For instance I use them as a sanity check to make sure the data lines up with what I expect, but it is an industry standard to jump as quick as possible into an inversion routine.

Also my first industry mentor an experienced mineral's exploration geophysicist who earned his keep during the pseudosection hayday showed me that the method of plotting a pseudosection for a dipole dipole array is inaccurate and skews the results

There is a better way of plotting the dipole-dipole pseudosection than the method demonstrated in the animation. The result is similar to a migrated seismic section (Poor man's inversion technique). The trick is embedded in how the wenner and schlumberger array pseudosections are plotted. Since I really can't divulge anymore than this I will leave it up to you to figure out how to plot the data.

In general I just don't think pseudosections should be stressed as much as they are. Other plots like multi-sounding or line plots of resistivity vs electrode position broken up by level tend to be more diagnostic. (standard in IRIS software and Res2dInv)

[lheagy]

Thanks @hal98x. I do agree that we should include more on inversion for DC (we have a couple notebooks that need to be integrated eg. ubcgif/gpgLabs#23) to demonstrate those concepts. However, I do think that pseudo-sections (or an appropriate variant for 3D) of DC data still are valuable, in particular for QC'ing data and post-inversion examining if and where there are regions that remain poorly fit. We are not advocating for interpreting from pseudosections, and perhaps we can speak to that further in the text, but using them as a tool to for visualizing data.

Right now, the gpg is light on other methods of visualizing data: there is a little bit on soundings, but that section could be expanded to include multi-soundings. We are in the process of organizing each of the methods (according to #47), and Data/ processing for DC would be a good place to expand on further data visualization techniques. In that regard, do you have any case histories that you think do a particularly good job of going through data visualization?

cc @dougoldenburg