40 years ago Longmire and Smith suggested that the soil characteristics, conductivity and permittivity, which vary greatly with frequency, can be fitted to universal graphs. The idea is if you know the values at one frequency you can predict the values at a different frequency. I've had their report for many years but only recently took the time to carefully evaluate the idea. Attached is a scan of the original report, Download Longmire and Smith scan, an EXCEL spreadsheet containing their equations compared to independent measurements, Download Longmire and Smith graphs , and my comments on their idea, Download Comments on Longmire and Smith . The idea has some merit but you should decide for yourselves!