How can I automate the sorting of pixels by shape (not by attribute) in a tif image?

Discussion created by michaeljosephdavis on Apr 3, 2012
I'm working on a collection of tif images downloaded from the USDA's Cropscape site, and my goal is to find all farms using center-pivot irrigation, which are indicated by circles on the map. Does anyone know of a tool or process in Arcgis 10 that could find these circles? There are many different values (crops) that are contained within the circles and they are not unique to the circles (See image attachment), so I cannot use a "sort by attribute" type of query. Any help or suggestions for a possible next step would be greatly appreciated!

Thank you!