Thanks to Andy and Jack for adding things I didn't cover. It has been over 40 years since I used one of the maps. In our area they located privies VERY easily once we got the hang of it. The measurement on our maps were very accurate for the most part but it true not all areas and not all years are the same. There is a definite learning curve. BTW, Rock did share the maps with others (for value received ) in distant locations as we had all we could do to dig all the pits in our areas.