Almost a Good App

As stated, the app lacks any instructions. Does this not function correctly because of user error? Maybe. So show me how to use it. The radius measurement would be an excellent and very useful tool for me if it wasnt so frustrating. It disappears at the slightest tap on the screen which means I cant explore around, nor zoom in or out without having to start over (to no avail) every time I touch the screen. Again, maybe its me, but without instructions, how can I possibly know that for sure? Please fix. This app has great useful potential.

BC Jackson about Range Finder Tool