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Ars Technica used a public records request to obtain a large dataset of license plate scans from 33 License Plate Readers (LPRs) in Oakland, California:
OAKLAND, Calif.—If you have driven in Oakland any time in the last few years, chances are good that the cops know where you’ve been, thanks to their 33 automated license plate readers (LPRs).
Now Ars knows too.
In response to a public records request, we obtained the entire LPR dataset of the Oakland Police Department (OPD), including more than 4.6 million reads of over 1.1 million unique plates between December 23, 2010 and May 31, 2014. The dataset is likely one of the largest ever publicly released in the United States—perhaps in the world.
After analyzing this data with a custom-built visualization tool, Ars can definitively demonstrate the data's revelatory potential. Anyone in possession of enough data can often—but not always—make educated guesses about a target’s home or workplace, particularly when someone’s movements are consistent (as with a regular commute).
It seems the cars of police officers, politicians, and others doing the spying should have been captured by the LPRs too. A prize for the first person to separate out what they've been up to...
(Score: 3, Informative) by Kromagv0 on Thursday March 26 2015, @12:51PM
One common thought that some have explored is to try and dazzle the sensor using LEDs [workingsi.com]. The thinking being that if you have some bright point sources of light they will flood nearby pixels making the plate unreadable. In looking into this some it doesn't appear to work all that well but in my opinion they just didn't take it far enough. Why try to flood the surronding pixles when instead if you just dump out enough IR over a large enough area you can mess with the camera's automatic exposure. My thought would be to build a larger license plate frame that has an area at least as big as the license plate and use a bunch of nice high output IR LEDs [digikey.com] for maximum effect. I want to get something that is putting out close to 1KW/m^2 of IR so it is like having the sun shine into the camera.
The most effective way of defeating ALPRs seems to be with license plate covers, or coatings you put on your license plate, the legality of these varies by state though. For example in Minnesota state statute 169.783 Subd. 7 [mn.gov] states
All plates must be (1) securely fastened so as to prevent them from swinging, (2) displayed horizontally with the identifying numbers and letters facing outward from the vehicle, and (3) mounted in the upright position. The person driving the motor vehicle shall keep the plate legible and unobstructed and free from grease, dust, or other blurring material so that the lettering is plainly visible at all times. It is unlawful to cover any assigned letters and numbers or the name of the state of origin of a license plate with any material whatever, including any clear or colorless material that affects the plate's visibility or reflectivity.
So that basically prevents all of the good known working methods. Also it makes most of those vanity license plate frames illegal as they cover part of the writing or tags, but that is selectively enforced.
So for me it looks like my best bet would be to try and force a massively underexposed image of the plate. Also for anyone else who is interested in exploring this further most new license plates are designed to be extremely high contrast in the IR spectrum and most ALPRs operate in IR, specifically the no red glow region. So the use of high output IR LEDs would appear to be the correct choice, although again depending on your state laws this type of illumination may be illegal, but it doesn't appear to be in Minnesota [state.mn.us]. Flashing seems to be the most regulated type of light from vehicles so be careful going down that route as well.
T-Shirts and bumper stickers [zazzle.com] to offend someone
(Score: 0) by Anonymous Coward on Thursday March 26 2015, @02:25PM
NoPhoto [nophoto.com] They are about to ship their 2nd generation. It detects the camera flash and flashes back its own high-intensity xenon light. Of course it only works when the camera uses a flash.
(Score: 2) by Kromagv0 on Thursday March 26 2015, @02:49PM
That is why I brought up the whole flashing and strobing thing. In my state those may not be entirely legal. Also depending on the xenon light and how it is aimed it may also be illegal.
T-Shirts and bumper stickers [zazzle.com] to offend someone
(Score: 0) by Anonymous Coward on Thursday March 26 2015, @02:32PM
My thought would be to build a larger license plate frame that has an area at least as big as the license plate and use a bunch of nice high output IR LEDs for maximum effect
Maybe these guys. [sunflexzone.com]
(Score: 2) by Kromagv0 on Thursday March 26 2015, @02:42PM
The digging that I have done seems to indicate that those devices aren't as effective as they are made out to be. They may or may not work depending on quality and dynamic range of the camera being use. When dealing with something like a cheap cellphone type camera they are easily fooled, especially while indoors. They do start having problems when illuminated by bright natural sunlight as those LEDs just don't put out enough power to overcome the sun, which is why I was thinking of getting something with the output in the 1Kw/m^2 range or better as that would mess with the cameras.
T-Shirts and bumper stickers [zazzle.com] to offend someone
(Score: 0) by Anonymous Coward on Thursday March 26 2015, @05:31PM
Ignoring the question of sufficient brightness, two engineering problems I see with that one:
(1) The mount is plastic, those LEDs have basically no heat-sinking, if they are bright enough to be effective they are also going to dissipate a bunch of heat. They will probably burn themselves out really quick.
(2) There doesn't seem to be anything protecting the led ribbon from the elements. Surely they could have come up with some sort of IR-transparent cover -- every tv remote control has got one.