ZZ Resistivity Imaging Pty. Ltd.
3.4 What are the exploration depth and resolution of the FlashRES resistivity meter?
These questions applies to all resistivity and IP meters. The exploration depth normally depends on the survey line length and maximum ABMN separations. Since the maximum ABMN separations for the FlashRES resistivity meter are the same as the survey length, the exploration depth for our resistivity meter is 20-25% of the survey line length. For example, if the user uses 64 electrodes and 5m electrode spacing, the total survey line length is 5m*63=315m. So our resistivity instrument's exploration depth is 62-79m.
The exploration resolution decreases with depth. From our experiences, the exploration resolution is about 10% of depth. The best resolution is 1/2 electrode spacing. For example, if the client uses 5m electrode spacing cables for a survey, its best resolution is 2.5m and the exploration resolution at depth 50m is about 5m. This is just a rule of thumb.
If the client wants to find a 1m diameter pipe at a depth of about 2m, it is recommended to use 1m or 2m electrode spacing cables, rather than over 2m electrode spacing cables.