I just did last weekend. I scanned the Cascade contour map, and did an overlay in Google Earth. I set some points and used my GPS to locate them in the field. Then shot points to bring back to GE to see how accurate it was going the other way. Actually worked out well. The area is an area I thought would have trout...and sure enough it did, in fact we didn't catch any perch...only trout, and all nice ones. So I think the process works well.