Monday, August 07, 2006

While a Canadian politician's recent claim he was not speeding in the vicinity of a stationary emergency vehicle may very well be true, his reason is weak. He claims mirrors from the emergency vehicle may have affected the radar reading.

Stationary mirrors by themselves cannot effect a Doppler radar speed reading because the mirrors are not moving. The mirrors are merely just (more) reflective ground echoes. Doppler radar, by design, measures moving objects and ignores stationary echoes.

The Royal Canadian Mounted Police (RCMP) officer that issued the citation stated he locked the politician's van speed (88 km/hr = 55 mph) when it was beside the police cruiser (range from radar is 0 or less -- negative range).

Vehicles beside a radar produce a speed reading of 0 (cosine effect and radar sample time limiting factors). Speed should be locked only when the target vehicle is in front of the radar (about 50 ft = 15 m or MORE depending on variables). It is possible the radar measured another vehicle in front of the radar and behind the politician's van.

CopRadar