Map rendering for navigation systems

摘要

When map data is to be processed for display in a mapping or navigation apparatus, the application processor (705) of the apparatus first checks to see whether any existing data in a local cache memory (706) represents a similar map part to the new data that is to be processed. This is done by means of a similarity analysis (601). If the map data already in the cache (706) is determined to be sufficiently similar to the map data that is to be displayed, new map data from a main map storage (230) is not loaded and processed, but instead the existing data in the cache (706) is processed for display of the map part in question. This has the benefit of a reduced system load, since already processed data does not need to be reloaded and reprocessed.

主权项

1. A method of rendering a map for display on a mapping or navigation apparatus, in which the map is rendered for display by loading data representing particular parts of the map to be displayed from a main map data store for processing and for display by a rendering processor of the mapping or navigation apparatus and the rendering processor of the mapping or navigation apparatus has a local memory in which data representing particular parts of a map to be displayed can be stored, the method comprising:
determining, when data representing a new part of the map is to be processed by the rendering processor for display, whether a part of the map for which data is already stored in the local memory is similar to the new part of the map to be processed, wherein the similarity determination uses a function that calculates a relative error between the already stored map part and the new map part and then determines whether the relative error is below a selected threshold value, wherein the selected threshold value increases as the distance from a viewer of the new map part that is to be displayed increases; and reusing data for the existing part of the map stored in the local memory for the rendering processor for displaying the new part of the map, upon the determination that a part of the map for which data is already stored in the local memory for the rendering processor is sufficiently similar to the new part of the map to be processed.