A method of processing data at a server 302 for maintenance of a database 516 of points of interest, such as speed limit enforcement devices. Each of the devices represented in the database has at least one attribute and a confidence value indicative of the accuracy of the at least one attribute associated therewith. The confidence value is time dependent and varies according to a predefined decay function. A report 500 relating to an attribute of a speed limit enforcement device is received at the server 302 from a mobile device 200. The confidence value associated with the speed limit enforcement device is adjusted in accordance with the received report, and information relating to the speed limit enforcement device 520, 522 is selectively transmitted to the or another mobile device 200 based on the confidence value.