What is "Trail O"? Trail O is a course designed to be viewed while walking along trails. Viewing stations are set up and marked on the map. At each viewing station several controls are visible (from 2 to 5). The feature is circled on the map and you have to decide which control flag is the correct one. You cannot walk into the woods for a closer look. You can walk along the trail to view it at different angles but must stand at the viewing station to pick which flag (counting from left to right, call them A, B, C, etc.) It's not as easy as some people think when they first hear about it but it develops your skill at map reading and is just fun to try.