A method for enhancing visual realism of an image of a geographical area displayed by an image display system which includes an elevation database and a polygonal terrain database of the geographical area in which the terrain features are represented by polygon faces having a constant normal vector across their entire extent, the method including the steps of:
- replacing the constant normal vectors of the polygonal terrain database with non-constant normal vectors derived from a higher-detailed terrain database of the same geographical area, to thereby produce a modified polygonal terrain database;
- and,
- using the modified polygonal terrain database, in conjunction with the elevation database, to generate an image to be displayed by the image display system.