Comment by mikeash
14 years ago
The law is not applied equally in court. By design, defense faces a much lower bar than prosecution. It is perfectly reasonable to require certified calibration to determine guilt, but accept data from an uncalibrated consumer device to overturn a ticket.
(As an aside, I don't think GPS would require any calibration anyway. If I understand it correctly, it'll pretty much either work or not work, with the accuracy of the output determined largely by atmospheric conditions and satellite geometry. The worry here would be deliberate tampering rather than calibration.)
There are other factors that can affect the accuracy of GPS; for example, receivers tend to be significantly less accurate in a CBD with lots of tall buildings. I've also seen receivers with an error before, eg. one that consistently reported itself as being 150m south of where it really was.
But I agree that by far the more significant problem would be deliberate alterations to the data. It doesn't seem like it would be particularly hard to do so...
At which point you're entering the realms of perjury, and probably several flavours of fraud, contempt, and other things that judges tend to dislike.
You're probably better off just paying the ticket.
Agreed, I'm not suggesting it's a particularly compelling option to deliberately falsify data for a court, but it could affect whether or not the court can consider GPS data to be sufficiently accurate - ie. even if the data is legitimate, how can the court know that's the case?