A synthetic rendering of the
terrain within a selected
field of view is created from raw
terrain elevation data, and the resolution of the rendering is proportioned to the altitude
above ground level (altitude AGL) of the aircraft. All the data points are subdivided into tiles. Only data from tiles within a prescribed
field of view are considered for
processing; all others are ignored. Within the selected tiles, only some of the
terrain elevation data points are passed to the
graphics processor for rendering. At maximum resolution, when the aircraft is on the ground or at a
low altitude, there are relatively fewer tiles within the
field of view and the fraction of the data points from each tile within the field of view passed for rendering is relatively large. As the aircraft's altitude AGL level increases, the field of view also increases in area increasing the number of tiles within the field of view. However, the number of data points forwarded for rendering by the
graphics processor is kept approximately constant by selecting progressively fewer and fewer
terrain elevation data points from each tile for rendering as altitude AGL increases. Only the data points that lie within tiles inside a prescribed field of view are forwarded to the
graphics processor for rendering. Once the tiles have been selected, the
terrain elevation data points are grouped in groups of a size that depends on altitude AGL, with more terrain data points in the grouped as attitude increases. Preferably the groups are triangle strips. Only the highest elevation from each group is passed to the graphics processor for rendering.