[aprssig] APRS speed and Cosine Rule?

[Rusty Bryant]

 Bob,

If you want me to keep you safe I'll say YES, but the reality is, most radar units in police cars do not use a cosine rule.

Part of our training is that we should keep a 10 degree or less angle between our unit and the target.  

But, any increase in angle will only benefit the suspect.  If they are going 30 mph over the speed limit and our radar indicates that you are only going 20mph over the limit, then you just got away with the 10mpg delta.

Just remember this, when you double your speed, you quadruple the impact force if you crash. 

Speed Kills!

Rusty
WB4BSD

    On Monday, June 8, 2020, 4:07:49 PM EDT, Robert Bruninga <bruninga at usna.edu> wrote:  
 
 APRS speed related?

Have cop radars implemented the Cosine rule?  IE, it should be possible to
include a magnetic compass in a handheld radar gun and to initialize it in
the direction perpendicular to the road with just a button push...

Then the gun can display the actual speed using the cosine rule as the cop
sweeps to keep up with your car, (or statically when the cop is at an
angle to the line of approach) and not just the relative speed (which
approaches zero) as the car goes past the perpendicular point.

Curious as to whether I need to consider this when speeding past a
radar...

Bob, WB4APR

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