I've never used them for mapping , miles away from me , I've read many a post about them , as far as I can read ( between the lines ) is there work is ok if not good , but there rollers give a very unrealistic reading ? Huge gains etc , then took to another rr and the figures are a lot less , don't be worried about figures , look at the map , you want a safe useable remap , no det , etc , and if your happy well that's what matters , they have to be half decent as they have been around a while . You will never keep every one happy ,