Are radar guns accurate for boat speed?

[MikeMischnick]

Hi,

This is the radar gun I use. There were two of us checking speeds of Open gas mono's this weekend The guns varied (+ or - 3 MPH)

https://www.ebay.com/itm/Radar-Gun-Baseball-Police-mph-Car-Speed-Velocity-Detector-Guage-Reader-LCD-NEW/192590405697?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

In my option a radar gun is a yard stick. If the gun is off by 10 mph it doesn't mater as long as its always off by 10 mph your using it to see if what you changed worked or not. I have been rely happy with the radar gun above.

Mike

 

[Terry Keeley]

A good way to "standardize" the angle error is to mount it on a tripod to shoot the transom and run straight down the front chute.

The angle is the same every time.

The actual speed depends on the cosine of the angle, here's a calculator: https://copradar.com/chapts/chapt2/ch2d1.html