# Electrical resistivity tomography

1. Apr 13, 2013

### Johntoby

Hi all,
I have been searching the internet for explanations on the method of ERT, but they are in general extremely complex and contain very specific vocab that I'm not understanding.
Would somebody care to explain to me the method of ERT in language that an A Level student can understand?
Thanks very much

2. Apr 13, 2013

### mikeph

Say you have a "region" where you can't directly measure the conductivity inside. For example, a lump of rock that you don't want to drill into. A voltage is applied across two terminals at the edges, and the current is measured. From that, you know the total resistance between the two terminals. If you do this for a lot of different positions of the terminals, you can build up an image of the conductivity within the rock. Formulating an expression for the predicted current as a function of the terminal voltage/conductivity distribution is the first problem. To estimate the conductivity distribution from measurements of the current, you must solve the inverse of this.

In general you need to know calculus, some electromagnetism and a lot of inverse theory to solve it.