Abstract: An information system (1) including an input (2) for receiving data (5) indicative of one or more consecutive identifiers such a pair of consecutive identifiers (6) and (7) or an individual identifier (8). Each identifier (6) to (8) includes data (9) indicative of at least one geographical waypoint. A processor (10) is responsive to data (5) for defining for each identifier (6) to (9) a respective polygon indicative of a geographical region. This occurs such that any given geographical position within the polygon is associated with the defining identifier In the present embodiment, each polygon has one or more characteristics and the defining identifier includes data indicative of those characteristics.