radar gun? - Stromtrooper Forum : Suzuki V-Strom Motorcycle Forums
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post #1 of 15 Old 05-14-2011, 08:15 PM Thread Starter
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radar gun?

anybody ever check GPS speed against a calibrated radar gun (or some other very accurate speed measuring device)?
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post #2 of 15 Old 05-14-2011, 08:45 PM
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Towns around my area regularly have radar operated "YOUR SPEED IS" mobile kiosks parked at major entrances to the town to slow people down. They have always matched the speed on my Zumo 550 exactly.

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post #3 of 15 Old 05-14-2011, 09:15 PM Thread Starter
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That's good news. Put new guage faces on yesterday and wanted to check them with my GPS which I just got back from doing. Speedo reads about a good as one can expect. Prett hard to hold exactly at a certain indicated speed but I figure I am 1 mph slow of indicated between 35 and 60 MPH according to my GPS.
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post #4 of 15 Old 05-14-2011, 09:17 PM
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I have bounced my droids GPS against both the cars GPS speed and the speedo, and my GPS equipped radar detector, all against the "self serve" speed kiosks, which they put out on base all the time. All agree.

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post #5 of 15 Old 02-10-2012, 04:42 AM
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Usually pretty close. HOWEVER...

As a wielder of said RADAR for the past decade I have found that GPS can vary enough to put one in trouble when relied upon to "toe the line" so to speak.

RADAR is exact. The counting unit can take a speed out to the .000s digit. It never rounds up though. What the operator sees is the true ones digit- So 59.999 MPH will have a readout of 59 MPH.

GPS has too many variables. Just today I used a GPS app on my phone while riding and the best accuracy was 9'. Now I'm not a mathematician but even I know that +/- nine feet really won't have a bearing on overall speed calculations... unless I'm putting around at .5 MPH.

One thing about those RADAR trailers. There is an effect called cosign that reduces read -out speed compared to actual speed. The further the target object is away from the center of the beam-the lower the speed displayed. So this actually favors the driver in nearly all situations as most RADAR is not operated in a true head-on fashion.

So if your GPS jives with a RADAR trailer on multiple occasions approached at a relatively centered angle, then you are probably safe.


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post #6 of 15 Old 02-10-2012, 09:07 AM
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Quote:
Originally Posted by TnTJ View Post
RADAR is exact. The counting unit can take a speed out to the .000s digit. It never rounds up though. What the operator sees is the true ones digit- So 59.999 MPH will have a readout of 59 MPH.

Things must have changed since my days in motors. All our manuals from the various manufacturers used to say +/- 2mph was the margin for error. That was in the basic operator course too.

Last edited by 10-95; 02-10-2012 at 09:09 AM.
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post #7 of 15 Old 02-10-2012, 10:33 AM
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Checked against laser radar.......spot on.

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post #8 of 15 Old 02-10-2012, 10:38 AM
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Every time I've been tagged for a ticket, I've gone back and checked the GPS track log and what the cop wrote on the ticket was spot on.

And yeah, radar accuracy is much improved since I was a radar tech in the Navy in the late 60's.

-Tom (DL650AL2) (KA1TOX) (E-I-E-I-O)

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post #9 of 15 Old 02-10-2012, 12:02 PM
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Quote:
Originally Posted by tiller4me View Post
Checked against laser radar.......spot on.
Do you mean laser and radar? Or a LIDAR device? Which is laser only.

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post #10 of 15 Old 02-10-2012, 10:44 PM
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Quote:
Originally Posted by 10-95 View Post
Things must have changed since my days in motors. All our manuals from the various manufacturers used to say +/- 2mph was the margin for error. That was in the basic operator course too.

It may have or it could just be the anal agencies I have worked for. Last one had the RADAR tech come out at a minimum every 2x/ yr and do the "super-duper/ can't be beat ever in court/ look how accurate we tech geeks can make this" calibration where they would show the counting unit go out to the x.000s digit. Had to check calibration w/ tuning forks prior/post every shift and if it wasn't exact we couldn't use 'em. But I do recall some manuals having a MOE for those checks.

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