Legality of speed camera position?

[Max Preload]

Cosine error is always advantageous to the person being tracked.

Not true for mobile speed cameras because they have a factor applied as they are intended to work at an angle to the road. Assuming that when correctly set up at the 22½º to the traffic flow direction they give the correct speed, if set up at less than that angle, the reading will be higher. Conversely if set at an angle greater than the correct, the reading will be lower.

[pete376403]

Ok so if you are pinged by a mobile camera is there any way of questioning in court the accuracy or otherwise of the camera angle setup?
ie in the way that calibration certs can be requested for car radar or speedos?

[Max Preload]

Ok so if you are pinged by a mobile camera is there any way of questioning in court the accuracy or otherwise of the camera angle setup?
ie in the way that calibration certs can be requested for car radar or speedos?

Highly unlikely.

[marty]

Not true for mobile speed cameras because they have a factor applied as they are intended to work at an angle to the road. Assuming that when correctly set up at the 22½º to the traffic flow direction they give the correct speed, if set up at less than that angle, the reading will be higher. Conversely if set at an angle greater than the correct, the reading will be lower.

so I say it again - cosign error is always advantageous to the vehicle being tracked. It could possibly be the calculation AFTER the event that disadvantages the tracked vehicle - in the unlikely event that the calculation was incorrectly applied - but the fact still remains, cosign error is still to the tracked vehicle's advantage

[gatch]

[B]On a serious note - under our law a passing lane is not a speeding lane. It is only there to allow vehicles to pass other vehicles travelling under the speed limit.

Yep, I know this much. I got ticketed by a man with a radar gun doing 113 passing a car.

Do'h.

[miloking]

- in the unlikely event that the calculation was incorrectly applied - but the fact still remains, cosign error is still to the tracked vehicle's advantage

In the "unlikely event"...lol you sound like one of those safety videos on the plane, yet planes do crash from time to time and we hear about it, however i havent heard about camera van with incorrect cosine formula applied because nobody cares that "peasants" think(know) its shady business as long as it earns money...

[Max Preload]

so I say it again - cosign error is always advantageous to the vehicle being tracked. It could possibly be the calculation AFTER the event that disadvantages the tracked vehicle - in the unlikely event that the calculation was incorrectly applied - but the fact still remains, cosign error is still to the tracked vehicle's advantage

No, it's not. The calculation is fixed on the angle of 22½º DURING the measurement - it's not applied after. That is to say the unit is calibrated to be correct at an angle of 22½º but the unit may or may not actually be at that angle. And if the angle is shallower then the registered speed is higher because the velocity toward the camera is higher at it's peak (the measured speed changes constantly while the vehicle is tracked, again due to the angle)

And it's COSINE.

[Max Preload]

Think of it this way: if you drove at 100km/h almost directly toward the microwave speed measuring device that is calibrated for you to be driving at a 22½º angle to it, will it indicate higher or lower? Higher of course. That is exactly the same effect as it being misaligned and the beam being directed more parallel to the roadway.

[davereid]

I must write in a bigger crayon so people actually read it ! From pg 2 of this illustrious and misinformed thread..

As you point out, its the angle of the camera to traffic flow.. not the angle of the van. But it still needs to be set accurately.

Its a common error to assume cosine error is always in favour of the driver, and for radar that is pointed directly at the target it is the case.

But I understand that speed cameras slant across the road. So Cosine error for speed camera radar can work against the driver.

This is because the radar is not direct - it is at an angle across the road, and it does not observe the vehicles true velocity. It observes velocity towards the camera, and uses trig (cosine) to determine the actual velocity.

The camera, if pointed more towards the flow of traffic will overestimate speeds. If pointed more across the road it will under-estimate speeds.

Look at it this way.

If the beam is shone directly across the road, vehicles will cross the beam with no velocity towards the camera.

If the beam is shone at 45deg down the road, the cosine of 45 is .707. So a vehicle travelling at 100 km/hr will have a velocity of 70 km/hr towards the camera.

Thus, if the camera is designed to slant across the road, it has to do math, to "see" 70.7 km/hr, but record your speed as 100, as thats your actual speed.

But, if the camera is aligned pointing down the road directly at vehicles, it will see a vehicle doing 70.7 km/hr, and will record 100 km/hr.

[marty]

i know it's cosine. i'd had a long day forgetting to set up 22.5 degrees accurately

[marty]

Think of it this way: if you drove at 100km/h almost directly toward the microwave speed measuring device that is calibrated for you to be driving at a 22½º angle to it, will it indicate higher or lower? Higher of course. That is exactly the same effect as it being misaligned and the beam being directed more parallel to the roadway.

Well the next time you pass a camera van i suggest you stop, get out and say


'CAMERA VAN MAN. NO I SUGGEST YOU TAKE YOUR FLASHING PHOTOGRAPHY EQUIPMENT AND SHOVE THEM UP YOUR ARSE, UNLESS OF COURSE YOU HAVE SET THE COSINE ANGLE CORRECTLY, IN WHICH CASE I WILL CARRY ON MY GOOD WAY MUTTERING TRIGONOMETRY EQUATIONS UNDER MY BREATH AND KNOWING THAT IF I SHOULD EVER BE UNFORTUNATE ENOUGH TO BE THE RECIPIENT OF A SPEEDING CAMERA TICKET, THAT I WILL DEFEND IT TO THE ENDS OF THE EARTH ON THE BASIS THAT YOU HAD NOT SET UP YOUR EQUIPMENT TO THE NOMINATED PARAMETERS'

let us know how you get on

[Max Preload]

Well the next time you pass a camera van i suggest you stop, get out and say


'CAMERA VAN MAN. NO I SUGGEST YOU TAKE YOUR FLASHING PHOTOGRAPHY EQUIPMENT AND SHOVE THEM UP YOUR ARSE, UNLESS OF COURSE YOU HAVE SET THE COSINE ANGLE CORRECTLY, IN WHICH CASE I WILL CARRY ON MY GOOD WAY MUTTERING TRIGONOMETRY EQUATIONS UNDER MY BREATH AND KNOWING THAT IF I SHOULD EVER BE UNFORTUNATE ENOUGH TO BE THE RECIPIENT OF A SPEEDING CAMERA TICKET, THAT I WILL DEFEND IT TO THE ENDS OF THE EARTH ON THE BASIS THAT YOU HAD NOT SET UP YOUR EQUIPMENT TO THE NOMINATED PARAMETERS'

let us know how you get on

It should be "OI! CAMERA VAN MAN! NOOOOO!".

Am I to take it that, despite all efforts to explain the undeniable logic, being that the COSINE effect does not always benefit the vehicle when a fixed factor is applied to a target return for correction to achieve a reading, that you still deny this?

[marie_speeds]

I have a headache now..... Angles, arses, cousins and cameras all very confusing

[Max Preload]

I have a headache now..... Angles, arses, cousins and cameras all very confusing

Don't worry. You just stay in the kitchen dreaming about kittens and looking pretty!

[davereid]

Well the next time you pass a camera van i suggest you stop, get out and say 'CAMERA VAN MAN. NO I SUGGEST YOU TAKE YOUR FLASHING PHOTOGRAPHY EQUIPMENT AND SHOVE THEM UP YOUR ARSE, UNLESS OF COURSE YOU HAVE SET THE COSINE ANGLE CORRECTLY, IN WHICH CASE I WILL CARRY ON MY GOOD WAY MUTTERING TRIGONOMETRY EQUATIONS UNDER MY BREATH AND KNOWING THAT IF I SHOULD EVER BE UNFORTUNATE ENOUGH TO BE THE RECIPIENT OF A SPEEDING CAMERA TICKET, THAT I WILL DEFEND IT TO THE ENDS OF THE EARTH ON THE BASIS THAT YOU HAD NOT SET UP YOUR EQUIPMENT TO THE NOMINATED PARAMETERS'
let us know how you get on

Seriously Marty,

If you are telling us that mobile speed cameras are not carefully angled down the road because police think cosine error is always in the motorists favour, then police will be paying all the money back...

The maths is correct.

A slant beam camera MUST be carefully setup, with regard to angle or it will either decrease or inflate speeds. Of course, if a record of the camera setup is not made, all tickets issued by that camera will be suspect.

I don't have time now.. but I will calculate an error chart. Is the correct angle supposed to be 22.5deg ? Is that from the roadside ?