DATABASES FOR CARTOGRAPHY AND NAVIGATION

Maps and charts have traditionally been used for navigation since the origins of cartography. In the digital cartography era, navigational use provides the strongest of motivations for database-driven map and chart production, for reasons of security, ease and regularity of update and ability to support both graphical and digital products. Navigational data, for land, sea and air, is also an activity where standardisation has, of necessity, had the most impact to date. The paper describes the particular requirements of digital cartographic databases for navigational purposes. A key area is that of update, both for atlases and charts and for navigational data. The later has a rapid update cycle requirement, matching that achieved by conventional means such as Notices to Mariners. Update requirements may be quasi-immediate (eg. in military applications) or quantised to approximately weekly updates (as in maritime navigation) or to formally defined changeover cycles such as the 28 or 56 day cycles used in air navigation. As well as implementing such update regimes for navigationally significant information delivered in digital form, th