Be sure to eat grilled carrots before you dowse. They give +2 perception, which increases the range of metals you can detect. There should be some spares in the Food chest inside the Flaxworks compound.
I've been dowsing around the camp at 16 coordinate intervals from east to west between 1360 and 1280, moving north by 16 coordinates when I finish a row. I suggest following this pattern, or something similar. --Kheti