A resistance survey measures the subsurface variation in soil resistance by passing a current into the ground through two electrodes and measuring the voltage between a second pair of electrodes on the ground surface. The resistance of the earth is dependent upon properties that include the soil compaction, saturation, mineral content, and porosity of rocks and other materials. Resistance surveys can map features where a distinct change in these properties occurs, including pits, trenches, foundations, compacted or disturbed surfaces, and changes in soil type. For example a humic filled pit excavated into a background of well-drained sandy gravels, covered by topsoil provides an example of a feature of relatively good conductivity (low resistance) within a background of poor conductivity (high resistance). The current flow concentrates through the pit fill in preference to the higher resistance of the sandy gravels due to the compaction, saturation level, and mineral content of the fill material. A corresponding disturbance in and around the area of the pit can be measured at the ground surface.
See What Meg Sees: Instructions for Interpreting the Data
Using the tool below, click on individual grids for a closer look at the Resistivity data Meg and her team gathered at the Dillard site. You can toggle between an arieal view of the landsape, the map of the data only, and then read Meg's interpertation of each of the data points as you learn more about what each grid reveals. Each grid you click on will become highlighted.