City parking enforcement uses GPS to determine where a parked vehicle is located. GPS is only accurate to within 10 feet under the best of conditions. Buildings, etc., can affect that accuracy and the fact that the equipment being used may not be able to hold those tolerances you will find, if the parked car left and then came back, and then parked close to where it was originally parked within the two-hour period, that the monitoring equipment will say that it was never moved. We saw that in an article in the Coeur díAlene Press that stated a motorist was cited when his vehicle was, in fact, parked the second time on the other side of the street from where it was originally parked.
To meet the letter of the law you have to show CONTINUITY. In order to issue a citation you have to prove that the vehicle was there for the entire two hours without being moved. That means that the equipment being used to monitor the vehicle in question has to pass that vehicle at least every 20 minutes if not sooner. I doubt that traffic personnel are driving past the same location that often, or that the equipment being used actually records that the vehicle in question is still there each time they pass, and keeps that fact as a record that can be used in a Court of Law. The program must be able to survive in a Court of Law.