Safe Speed Forums

Some countries (excluding the UK) allow a cosine error correction to be programmed into the equipment. If the correction is 'overdone' then it can work against the motorist.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
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I'm sure the partnerships would love that one!!!

The other way it can work against the motorist is if he is caught coming out of a hollow to a fixed gun - the beam rides along the bonnet from the back - sli rule - extra 10 mph approx worst case.

Yeah, except that's slip effect and we were talking about cosine error.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

How does the device work out the angle involved?

It doesn't. Someone programmes it in having done some dead reckoning and then a calculator does the division by the cosine of the angle.

What angle?

I think I might be confused here. I can see this working with fixed installations, but not with laser devices which must be tracked with the target to avoid slip. Therefore the angle is continulally varying and as such programming one angle in would be meaningless. This is (or was) a thread about laser devices.

None of the laser devices I have used have any mechanism for programming anything into them whilst being operated.

If true it's a totally bonkers idea for lasers. At most reasonable operating distances, the cosine of the angle involved means that any effect is negligible (less than one tenth of a mile per hour).

Some of the LTI 20.20s I've come across allow you to change the near and far thresholds, which means that to all intents and purposes, any real error can be prevented.

For fixed installations I can see it working a bit better - but why bother with the complexity when normally you don't prosecute until speed is some way above the limit (5-10mph). Such a tolerance pretty much eliminates the need for any cosine correction.

Without cosine correction, any error is in favour of the driver - so why complicate the matter with something than can give rise to legal complication?

Can you give any details of what devices allow this? I'd be interested to look into how they work and learn a little.

Thanks.

I agree. I would assume the operator would be prohibited from targeting a vehicle before it reaches the entered angle (or calculated distance given the geometry of the setup).


I’m sure there are operators who target at angles of greater than 3 degrees (resulting with at least one tenth of an mph at 70), but I agree that the angle would have to be huge before any significant error can occur.

I don’t think the UK camera partnerships will want UK alleged offenders requesting proof of set-up each and every time; this could be the reason why our models don’t have this feature.

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

smeggy wrote:

I don’t think the UK camera partnerships will want UK alleged offenders requesting proof of set-up each and every time; this could be the reason why our models don’t have this feature.

all this is recorded on the operators notes summary sheet, pocketnote book (if used) or whatever system the SCP uses for recording the required checks