[DougWebb]

If I were implementing this for NASA, I'd run the analysis a number of times using different patches for my samples. Any areas that come up as anomalies more than once are probably worth checking out.

You can choose patches randomly, but they probably also have good enough telemetry and modeling to be able to predict which areas in any given picture are going to show part of the rover. That data can be used to ensure that your random patches don't include rover parts.