screeech wrote:

And for the record...the patrol speed on the radar IS established by the radar unit itslef, not by the cars speedometer or the V.I.P. (portal, not protocol)

Hmmm. The radar instructor was pretty explicit in his explanation to me. I thought I understood him but maybe not so can you elaborate?

1. How radar units establish patrol speed?

2. What does VIP do, how it does it work and why is it used?

3. What is shadowing?

4. Does shadowing occur with VIP equipped units? If not, why not?

jsherk wrote:

rank wrote:

The radar instructor explained to me that this is because the radar uses Vehicle Interface protocol". He went on to say that VIP means the radar is tied to the cars ECM therefore it doesn't matter what the speedo says.

Wow, this is important... I had always assumed that the patrol speed displayed on the radar unit was calculated using the radar itslef.

Units without VIP establish patrol speed with the radar. They use large stationary objects (like bridges, tractor trailers) and a point of reference to establish a speed of zero....whoops that's right sometimes they can use a moving tractor trailer to establish "zero" which throws the radar off. This is called shadowing and the big advantage to VIP.

jsherk wrote:

rank wrote:

If the patrol speed on the radar unit is tied to the ECM then of course it will always be almost exactly the same as the speedometer... they are both getting the same number from the cars computer!

Yep. That's the way it was explained to me.

jsherk wrote:

rank wrote:

This to me is even more of an issue because you still have no way of knowing if the ECM computer reading is accurate or not. So it goes back again to getting calibration/accuracy records of the speedometer (or ECM computer as the case may be).

Again you can not say the radar is accurate because it matches the speedometer/ECM and the speedometer/ECM is accurate because it matched the radar... you need an independent test of one of them to prove it is accurate before you can claim the other is also accurate.

I agree. I think I mentioned before that I operate a small fleet of highway tractors. I have the software to program the ECM's The speedometer only knows what data is typed into the software. I can change the "patrol speed" by simply changing the tire size or rear gear ratio in the software. Therefore I contend that it's possible the patrol car has different sized snow tires installed and it may be throwing the patrol speed off and nobody would know/care because it says right in the test procedure that "the radar is assumed to be correct". Details like this is why the people need to see the COMPLETE manual.

And by the way, IMO, withholding this information from the defendant, the taxpayer, the people that bought and paid for the manual is not justice and should be heard by the supreme court if someone wanted to take it that far. You have the right to cross examine your accuser and in the case of Radar/Lidar the machine is your accuser. The officer does nothing but write down what the machine says.

The moving radar establishes its patrol speed using the front or rear antenna. It does not obtain the patrol speed from the VIP.

I'm not currently in reach of my VIP manual to quote from it though.

Decatur, you are correct: the patrol speed is established by the radar beam leaving the antenna and striking off stationary objects such as the ground in front of the cruiser...with shadowing, the patrol speed on the cruiser is established off the back of a moving truck, going in the same direction. The cruiser must be going faster than the truck to its front...with the v.i.p., shadowing will not occur, it was a fact of life before the v.i.p. thing came along...but even with shadowing, a properly trained radar operator would recognize the fact and disregard any readings during a shadowing event...there is lots more to be said on it, but that is basically it...

And to clarify: All patrol speeds are obtained through the radar, with or without the v.i.p. plugged in...

What does the v.i.p. plugin do?

jsherk wrote:

What does the v.i.p. plugin do?

Exactly. And how does the VIP eliminate shadowing?

The OPP instructor and I discussed this at length and I thought I understood it. I suppose I'll have to get another speeding ticket so I can sit with him again and review the manual. Maybe he'll just get tired of me and make me a copy LOL.

I would think that the people that allegedly use this device would know what it plugs into. Voila. The big mystery is solved.

"The VIP™ is a compact module that plugs into the diagnostic port of the vehicle improving the performance of the Genesis II Select™ radar. The VIP™ reads the speed information sent by the diagnostic port and uses that information to help eliminate shadowing......"

"Decatur VIP Speedometer Interface Kit will assist the radar in providing an independent estimate of ground speed, which will essentially cure shadowing and batching..........Decatur Speedometer Interface Kit VIP works in all cars made after 1996........Vehicle-independent through the diagnostic port inside the car......Genesis radar accepts patrol speed information through communication port"

Good find

This does infer that the patrol speed displayed on the radar device is still determined by radar though.

I checked prior posts and I don't think anyone actually asked what it plugs into.

And to clarify one of the highlighted areas, the Genesis radar does accept patrol speed through the VIP but it doesn't establish the patrol speed through it. It's merely a check and balance for the patrol speed. Eg. Radar without the VIP may have trouble keeping up with an accurate PS if the vehicle is accelerating heavily. The VIP ensures this won't happen. It is still the officers responsibility to make sure the PS and speedometer are within the proper range prior to accepting a target speed.

Post edited ....

Decatur wrote:

And to clarify one of the highlighted areas, the Genesis radar does accept vehicle speed through the VIP but it doesn't establish the patrol speed through it.

If the radar antenna still determines PS then how is shadowing eliminated by plugging in VIP?

jsherk wrote:

Good find

This does infer that the patrol speed displayed on the radar device is still determined by radar though.

Where do you see that inference?

I don't see any mention of the radar antenna being used to determine patrol speed in a VIP equipped radar unit.

To quote hwybear, "VIP (vehicle interface portal) is a feature that constantly correlates the patrol speed on the radar to the speedometer, which always ensures the patrol speed is accurate. This prevents batching and harmonic errors, plus also allows the radar to be operated in adverse weather conditions as the patrol speed can still be obtained"

Decatur wrote:

It does not obtain the patrol speed from the VIP.

Decatur wrote:

...the Genesis radar does accept vehicle speed through the VIP.....

Decatur wrote:

but it doesn't establish the patrol speed through it.

My head hurts.

Obviously, when you say vehicle speed you mean speed of the patrol car (not target speed). What then is the difference between the speed of the patrol car and "patrol speed". One would think they are synonomous. Are they not?

I would suggest that vehicle speed is target speed, patrol speed is cruise speed.

I don't have much experience with a VIP cable I'm guessing this is specific to Genisis II Select . However Stalker uses a VSS cable which I am assuming is the same as a VIP which does the following : (directly from Stalker)

Moving traffic radar systems measure the patrol car's speed by tracking the radar return off the road surface in front of the patrol car (ground speed). Occasionally a radar can be "mislead" when the patrol car is following another vehicle that is moving at a speed that is substantially different from the patrol car's speed. When this happens, the radar will see the speed differential between the vehicles and pick that as the patrol car's speed. This is called "Shadowing."

The radar may get signals from many sources while a patrol car is moving; ground speed, closure speeds from oncoming vehicles, and relative speed differentials of multiple vehicles ahead of the patrol car. Sometimes the radar just needs a little help in picking which speed is the actual ground speed. With conventional radars it is up to the operator to make sure that the radar has made the correct decision on which signal is the ground speed. The Stalker DSR solves the problem by using the VSS signal to tell the radar which radar signal is the ground speed.

All modern vehicles have a VSS sensor (Vehicle Speed Sensor) attached to the transmission or an axle that generates a speed signal. This signal is used by the speedometer, cruise control, and some of the engine and transmission computers. By tapping into this electronic signal the Stalker DSR can monitor the patrol vehicle's speed as measured by the car's VSS sensor.

Once the VSS cable is wired and attached to the Stalker DSR, and the radar is operated in the moving mode, the DSR performs an "Auto-Calibration" sequence. This sequence matches the VSS signal to the radar ground speed. This patent pending automatic synchronization routine overcomes concerns that tire wear could impact accuracy and allows the radar to be effortlessly switched betweens vehicles.