Re: Derbyshire - helicopter speed enforcent?

Mark Foster wrote:
> In article <_NvKe.5193$3N4.702@xxxxxxxxxxxxxxxxxxxxxxxxx>,
> "Steve" <steve@xxxxxxxxxx> wrote:
>
>>> I would guess laser is ineffective at that range and from a moving
>>> platform, and gatso-like double pictures would be difficult to get
>>> the resolution for.
>>
>> I can do more than guess, Laser and Radar CANNOT be used from any
>> moving vehicle. Nor can it be used from behind glass.
>
> Bzzzt. Wrong answer.
>
> Whilst that may be true from a legal standpoint in this country (I
> don't know, others may be able to answer) it is certainly not true
> from a technical standpoint.

I don't know about the legalities, but I presume that radar and laser can
only measure the component of speed in the direction of the beam. From a
following police car the speed measurement is in the same direction as
travel, so no problem as long as the police car has a calibrated speedo.
>From a helicopter hovering above, you would need to compensate for the
vertical and horizontal angles between the helicopter and the target
vehicle. I imagine the speed gun would have to be linked to the helicopter's
GPS and attitude sensors to do this. There could also be issues with
vibration making it difficult to pick out individual cars, particularly at
busy times, so you might need some technical wizardry to cope with that.

All perfectly possible I'm sure, but it's far easier to paint some markers
on the road and measure time over fixed distance. There are fewer
calibration certificates to argue about, and it's easier for the law to
understand.


.

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