Citazione:
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Originalmente inviato da anfarol Tutti i sistemi a distanza (laser, ultrasuoni, audio, etc), per funzionare ed ottenere un rilevamento preciso, devono essere esattamente in linea. Se sei angolato, non funzionano o non sono attendibili. .... |
Per compeltare quanto detto, riporto una parte del manuale linkato dall'amico Bartolini di una nota ed economica laser gun:
Q. Does angle effect accuracy or a radar gun? A. Yes, it does! Please note that the radar will not work properly if it is used as pictured above. The picture shows a race car traveling at the right angle to the radar beam. Such a situation should result in a reading of either zero MPH or only a couple of miles per hour. There is little or no relative motion towards/away from the radar source, hence no change in the frequency of the reflected beam received by the gun. This is how Doppler radar guns work: Target Speed equals the difference between the Transmitted and Received frequencies. The Bushnell Velocity Speed gun as any radar gun will measure the relative speed of a target as it approaches the Velocity. If the target is in a direct line (collision course) with the Bushnell radar gun the measured speed will be exact. As the angle of incidence increases, if you move either right or left of this direct line, the accuracy will decrease. The measured speed will decrease as you move off this centerline. This phenomenon is called the Cosine Effect. It is so called because the measured speed is directly related to the cosine of the angle between the Bushnell Velocity Radar Gun and the targets direction of travel. In Bushnell tests, a 12-degree angle did not effect performance much. The Bushnell Velocity Radar gun can achieve +/- 1-MPH speed accuracy to a baseball at 75 feet away at a 12-degree angle or less. A 20-degree angle at 60 feet away would result in +/- 3-MPH accuracy. For more information, please see Page 6 of Bushnell Velocity Radar Gun Manual that we provided for you. We highly recommend to use a baseball radar gun when you stand directly behind or in front of the pitcher!. "
Da qui si vede che un angolo di 20gradi, la misurazione è affetta di +/- 3mph (4,8Km/h), quindi per nulla poco. Scende poi a 1mph (1,8Km/h) con un angolo irrisorio di soli 12°.
Spero che sia informazione utile.