posted 02-08-2002 09:18 PM ET (US)
For targeting purposes.....Actually, the only way to determine the speed of the vehicle from the air is to run a stopwatch between a previously measured distance (from some foggy memory chip in my RAM, 1/10 of a mile rings a bell).
Some agencies paint lines on the road, some will place out along side the road, in the weeds, large fold out 4x4' squares for one day use....
The observer (and in real dumb instances, just the pilot) will note a potential speeder , and note the elapsed time, check their chart and radio down the direction, speed, color, model and make ("Hey MU2 ((MarkedUnit)), I've got a large Cadillac pullin a HUGE Whaler with twin Mercs that's just passed ME").
At that point, it's pull out the wallet time.....
As an aside, we've worked the bridge between Ontario and Michigan for kids speeding back across after the bars close with a state police laser unit. The night I worked had the evenings winner clocked at 68, coming down the bridge (it's a 35 zone, btw) and that laser unit is damned accurate. The troop would call out "68.3 mph for 837.5 feet".
After Customs or INS was done with their questions, they would get directed to one of eight waiting MU's.
Best - Don