Just FWIW, in the VN era the U.S. Army contracted for a automatic ranging scope. When the first scopes arrived, the troops found they were useless, showing the range as much less than it was. The contracting officer discussed the issue with the scope manufacturer but no one could figure out the problem. Then one of the soldiers asked how the ranges were calibrated. "Why by using the standard measurement, a six-foot tall man," the contractor's expert replied.
"I think I know the problem," said the soldier. "I spent a lot of time in-country and never saw a six-foot tall Vietnamese." The red-faced manufacturer hurriedly re-calibrated the scope.
Jim