There are several ways in which to preform map dowsing . All incorporate using a map or sketch of some sort.

Then by using a pendulum or rod over the map a dowser seeks a response for a desired target.

This is accomplished by using a ruler seeking an x , y coordinate or by gridding out the map , seeking a hit in a grid,

then zooming in a peticular grid , and redowsing until the desired accuracy is achieved.

"With a map or a sample sketch of the terrain, an individual property, whether a house lot less than an acre in size or a ranch of several hundred square miles, can be dowsed by one proficient in this method. Map dowsing is best performed not with Y or L rods but with a pendulum. One way is to overlay the map with a grid dividing it into rectangles (though this grid can be mentally pictured or imagined). The dowser then asks which rectangle(s) on the grid will contain the best site(s) for drilling a water well. The pendulum will supply the answer. Note that in the act of map dowsing, the dowser has transcended the limitations of space. The map can represent a property in a neighboring country or in a country halfway around the globe."