Buckinghamshire CC ANPR cameras

Roland Perry lists at internetpolicyagency.com
Sat Jan 7 09:27:21 GMT 2012

In article 
<AFD1C8AA-C7DC-4F81-A66F-C32CA7ED0B2A at sourcetagged.ian.co.uk>, Ian Mason 
<ukcrypto at sourcetagged.ian.co.uk> writes
>>> Is there a standard "depersonalisation" algorithm? If so anybody know
>>> what it is?
>> No. Indeed, in general, it is not possible to "depersonalise" and
>> retain any usefulness in the data.
>> So step 1 is probably to find out WTF they're actually doing.
>It depends. If they are strictly monitoring traffic flows and journey 
>times then all they have to do is assign a unique journey number to a 
>set of records for a vehicle and drop/delete the registration number 
>when the journey seems complete. Each time the vehicle starts a journey 
>it gets assigned a new unique journey number so that there's no link 
>with previous journeys for the same vehicle and no record of the 
>registration number at all once a journey has completed.

aiui the Trafficmaster system (blue cameras) works a lot like this.

>Obviously  there's detail to work through such as: a vehicle enters the 
>area, is  seen by ANPR on entry, then parks up for several days and 
>isn't seen  by a second ANPR camera; at what point do you delete the 
>partial  journey record that will, of necessity, still contain a 
>registration  number.

About an hour after last seeing the plate would be plenty if you are 
looking at the "flow" of traffic.
Roland Perry

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