I found this online and was curious if anyone had used a similar program before. If it is accurate it would be helpful for guys like me who don't have the money to drop on a high dollar range finder and shoot in open fields instead of measured flat ranges. It will even tell the elevation changes in a chart format that would be helpful in calculating scope adjustments.
Google maps has this capability natively. However, I think you'll find that for shooting any appreciable range, the error will be the cause of definite firing solution error. It does work to get close rather than just guessing. At any appreciable distance, an error of as little as 10yds will certainly show itself when computing firing solutions and comparing their prediction to real world fire.
I've done Google Earth distance calculator and like Orkan said its okay. The best way to use it is by marking to two points that don't move. So one tree to another.
GPS is the most accurate method I've used without an LRF. Go to the target, mark waypoint, go to firing position, then set a straight line course for the target waypoint. That is usually accurate within a few feet. A guy can get a cheap GPS for about $50.
@orkan back when I had a different jon I use to do this with my RTK rig. Sub inch accuracy, that's how the range was once marked out until people moved all the markers.