Thats very true.

But isnt this why officers typically give 5-10 over the PSL for small errors like this?

Bear just i have heard that alot of officers will say okay give you ten over for errors maybee with the radar or lidar and their speedometer.

But lets say you clocked someone for 152 km/hr.

Would you put this down to say 49 over (leaving some room for error). Or take it as it is at 152?

No, we do not use tuning forks for a good 4 years now.


Negative, no error with radar or lidar. Probably to allow the target vehicle speedometer to be out 10km/hr.




There is no error in the reading.

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Above is merely a suggestion/thought and in no way constitutes legal advice or views of my employer. www.OHTA.ca

Every radar and lidar device has a working tolerance of plus or minus 2 KMH.....It's on the specification page....Let's see here......http://www.pbelectronics.com/police_lidar_laser.htm

At the bottom of the page The Marksman ..............
Dimensions:3.5 in x 5 in x 8 in
Weight: 4.5 lbs
Speed Measurement
Distance: 30 ft to 3500 ft
Speed Maximum: +200 mph to -200 mph (accurate zero reading)
]Accuracy: +/- 1 mph
Acquisition Time: 0.3 seconds
Range Measurement
Distance: 30 ft to 3500 ft
Accuracy: +/- 6 inches
Acquisition Time: 0.3 seconds
Targeting
Pin-point beam (3 milliradian divergence, 3 ft wide at 1000 ft)
Adjustable illuminated red dot slight
AutoCapture triggering
Optional SpeedScope with in-scope data display
Power Requirements: 10.6v - 16v (12v nominal) 750 mA
Eye Safety: FDA Certified Class 1 (CFR 1040.10 and 1040.11)
Communication: 1/2 in adjustable illuminated display, RS232 Serial
Environment: -22 to +144 deg F

There is a margin of error........

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What all those specs don't tell you is that the unit rounds DOWN and COSINE that is where the plus /minus comes in.

When using properly, if a reading was 77.9km/hr it will round down to 77km/hr.....this is the PLUS reading.

When getting a reading, one can not be directly in front of the vehicle at the same height, therefore a cosine affect comes into play hence the reading is LOWERED from the true speed.

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Above is merely a suggestion/thought and in no way constitutes legal advice or views of my employer. www.OHTA.ca

How accurate are most speedo's in cars?

I heard alot of car speedo's are usually 3 km/hr faster then what your really going.

The cosine error comes into play at 10 degrees and up. If you shoot a beam, radar or lidar down the road 400 meters, you'd have to be 35 meters off the road inorder for there to be cosine effect and a lowered reading. If you are an officer sitting in the median taking readings, there is no cosine error. If you read through the users manual for any of the speed measuring devices it will state that the reading could be off by plus or minus 2, even in testing.

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Neo asked me to comment on his post/provide some advice which I will do here.

A couple of points on the Decatur Genesis VPD. You have to carefully read what is written AND what is not written in the manual!
Nowhere in the manual does the manufacturer state that this self test proves the device is working properly. Read the manual carefully. You will notice they go to great lengths to AVOID making this claim. What they do is provide a description of what happens when you press the button. But they carefully avoid connecting the test to any assurance that it constitutes sufficient proof that the device is functioning properly. (See Radar Identified's comments as well...)

This is the heart of the issue. Was the device working properly? I haven't seen any case law to suggest the self test button replaces the tuning forks or that independent testing is no longer required. Just because no one is doing it or the manufacturer removed it doesn't mean it works. Where's the proof?

***********************
The Antennae

I'm not sure I read 6.1 "Operator Requested Self Test" the same way. If there is a transmitter which tests a powered up antennae than yes, it's an electronic tuning fork. But if it only tests the signal processing component without transmitting to the antennae than no it's not replacing the tuning fork. I don't see wording to suggest the transmitter is being operated or signaling the antennae.

Even if it was the "new tuning fork", (let's call it the e-fork) don't forget, tuning fork calibration had to be independently tested from time to time. Which means the transmitter would have to be tested from time to time. But I'm not sure if there is a transmitter specifically testing the antennae. RI can you confirm this?

I've read the VPD Manual and I don't see any repair or maintenance guidelines at all. A device can't simply self test itself forever. What are the operating parameters and life expectancy? We can't simply put our faith into the device. The police services would have repair/maintenance/testing logs for this model. One device may work wonderfully, but the model rolled out to a police force will have a range of performance that allows them to predict faults and issue operating guidelines beyond what the manufacturer claims.

Before they buy a radar gun they would test it to see whether the manufacturer's claims are valid and whether the device truly is an improvement over other radar guns or the older tuning fork variety.

They should be doing the same kind of evaluation for anything they use. Like when they decided to buy a Charger as their new fleet vehicle instead of a Yaris. Imagine if the Yaris had a 425hp self test button that simulated the pistons moving up and down and the spark plug igniting. Would you believe it?

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Oh wait a minute... TC with this little thing you might've opened the door to stand speeding ticket prosecution here on its head:





Might be a game-changer. If the manufacturer does not specifically state that the test proves the device is working and accurate, then I think neo333 just got his defence right there. Now talking about the radar antenna. The way I read this...



...was that there was a built-in device that transmitted signals ("synthesized doppler frequencies") that acted as an electronic tuning fork, so to speak. But if it merely checks the processor and internal components, then yes I fully agree with you. My practical experience has been with weather radar and radar altitude-measuring ("radalt") equipment so there's a bit of a difference, although the principles are the same.

I had to do some thinking about this, and I really would have to look at the manual (are there diagrams available?). Thinking about radar theory and operation... I've come to the conclusion... that the regular old tuning fork test would actually be more reliable than the e-fork. Bear with me, this is going to be painful.

We know that radar works by sending a signal out from the antenna, signal bounces back, hits antenna, the time of the return = distance (due to known radar signal speed). Then frequency shift (Doppler effect) of return, through calculation = speed. But, the synthesizer would, if it does what I think it does, fire a pre-determined frequency at the antenna which is then picked up and analyzed. The frequency would be set to simulate the same frequency that a vehicle would generate if it were travelling at that speed. Here's the problem: At no point does the radar test an actual signal that was sent outbound from the antenna and then returned to the antenna. So we know the receiver is probably working, but how do we know the transmitter of the radar antenna (not the synthesizer) isn't improperly calibrated and generating an improper frequency that, upon reflection off a car, is giving a higher speed than the vehicle is actually travelling at? We don't! The only thing that would work is the tuning fork, which takes the outgoing signal, bounces it back, and this tests both the receiver and transmitter. The synthesizer is only testing one function of the radar antenna: the receiver.

Sometimes old technology is the most reliable.

(Sorry about the convoluted explanation. Just got home after a late Newark turn.)

Not bashing anything that was previously written but lidar devices do have a form of "antenna" testing. In order for the unit to properly gauge when the light pulse leaves the gun, a small portion of the beam is redirected into it's "timing" circuit. The radar gun may also do the same thing as a reference to the frequency shift it is looking for. We have to remember that there are a rather large number of sources of "noise" in the environment, so a reference is always needed. The gun would have to "know" what is being transmitted, otherwise every reading would be worthless......

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The LIDAR test I'm not familiar with so I really can't say. What we really need are some internal diagrams of the device (and more info about the synthesizer). As for the synthesizer changing the frequency of the outbound signal and returning it to the receiver, it is possible, although the way the Genesis manual is written, it doesn't appear that way to me. The reason being, it said "uses synthesized doppler frequencies." But I could be wrong.

Here we go:http://www.patentstorm.us/patents/5525996/fulltext.html

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I will definitely bring this up in court (if I have to proceed with trial that is).

However, I did find some case law with respect to external testing that does not support this argument.

See R. v. Laarakker 2008
Here is a quote:
" In the case before me today, Cst. Lamirante claims he tested the radar gun in accordance with the operator’s manual, which involved ensuring the radar was internally lighting up properly. Cst. Lamirante acknowledges this testing did not involve externally testing the radar with any object moving at a known speed. The instrument in question is an approved radar gun. Cst. Lamirante has been qualified to operate the instrument. If the operator is a qualified operator, and if the operation is in accordance with the operator’s manual, then this court is not prepared to make any presumption of impropriety with the testing of the radar in the absence of some expert evidence upon which to base a reasonable doubt as to the unreliability of that radar testing. To the degree that this ruling may be found to be inconsistent with the Broadway decision, I reject the Broadway ratio."

So does this mean I will bring in some kind of expert evidence? How do I do this? Or can I simply introduce a reasonable doubt by stating the concepts and issues Radar Identified and Ticket Combat have raised?
Thoughts?

The heart of the issue is the defendant Laarakker did not challenge the officer's assertion that he tested the device in accordance with the manufacturer's instructions. We ARE CHALLENGING that assertion! The officer is not testing the device according to the manufacturer's instructions because the manufacturer is silent on what constitutes proper testing. Laarakker did not say this. But you will, right?

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Fight Your Ticket!

If Neo's other post is any indication, he'll say it and much, much more.

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My case is closed without proceeding to trial, so never got a chance to bring this up. Maybe we can all help the next guy who is charged with a self-tested device and set a precedence.