Database for a navigation device, method of outputting a three-dimensional representation of a terrain and method of generating a database

A database (10) for a navigation device includes digital elevation model data defining a three-dimensional surface. The database (10) stores, for plural tiles of a tiling, a first array (23) including three-dimensional coordinates of vertices of plural triangulated irregular networks, TINs, for the respective tile, and a plurality of second arrays (24, 25). Each second array (24, 25) respectively defines triangular faces of a TIN and includes a plurality of vertex indices of the vertices to define triangular faces of the respective TIN. A method of outputting a three-dimensional representation of a terrain and a method of generating the database are also described.