In order to make the search for horseshoes easier, the map was divided into several areas. Nowhere in the game will you find any list of which horseshoes you have already collected, so it's best to move one area after another.
Each horseshoe has its GPS coordinates ([x,y]). Point [0,0] corresponds to the upper left corner of the map. The first value (x) goes up as you head to the right and the second one (y) as you go down the map. Therefore the largest coordinates are in the lower-right corner of the map, behind the golf course.