[s-cars] Speeding ticket technicality

[Igor Kessel]

Kirby Smith wrote:

 > I wouldn't invoke the cosine effect if I were you.  The measured speed
 > is the true speed times the cosine of the angle between the measurement
 > line of sight and your velocity vector.  In other words, you are going
 > faster than measured.
 >
 > kirby
 >
 >
 > "Varon H. Fugman" wrote:

 >>P.S. If he clocked you while you were coming around a corner, 
depending on
 >>where he was relative to you, there's always the possibility of the 
cosine
 >>effect.  This is where the straight-line closing speed between you 
and the
 >>oncoming police car is higher than your actual speed along the curve.
 >>
 >>P.P.S. And with moving radar one should also rule out shadowing...  Could
 >>there have been a large truck or train moving slowly that the radar could
 >>have mistaken for the ground?  This too can result in a higher than 
actual
 >>speed reading.  The officer is supposed to verify that the "ground speed"
 >>displayed on his moving radar unit matches his speedometer, but in their
 >>hurry to make a U-turn and pull someone over they frequently omit 
this step.
 >>Of course, that doesn't mean they will admit it in court!

I was just about to say that, Kirby. It is amazing how the engineers 
tend to think alike :)
The policeman measured the _projection_ of the velocity onto the 
perpendicular, which is by definition less than the actual velocity. 
Thus it would be a disservice to oneself to attract the judge's 
attention to this peculiarity. :)

-- 
Igor Kessel
two turbo quattros in the stable,
the third one in the works