For those planning vertical installations, I
found a nice full-color version of the FCC Soil Conductivity map
online. It's in html format, but most browsers should be able to
print individual pages for your own area:
https://worldradiohistory.com/FCC_Ground_Conductivity_Maps.htm
(Finding out my area is 2mS/m wasn't good news)
73...
Randy, W8FN