JAckerman

The Callaway GPS has a "mark" function.. Once you hit that you just hit your iron and start walking and it will tell you to the yard how far you just hit your last shot

Well my partner and I each have a gps.. one is a Callaway and the other is Garmin.. they both agree on yardages and they are close to the markers on our course.. So far no I phone has been close except once in a great while. Not sure many of you have done this comparison so check you phone against a know yardage marker and see how close it really is John