| 摘要 |
The moving map composer (MMC) is a device that allows a user to manipulate different sources of map data into a single map for presentation on a display. The MMC has an ability to extract a predetermined area of map coverage defined by sets of latitude and longitude points, or non-orthogonal areas of map coverage, the smallest of which is a segment. A bitmap is a representation of an available map coverage for a given area selected by a user having a "set", or "1" bit to indicate a segment is present, and a "clear", or "0" bit to indicate a segment is missing. The size of the bitmap is determined dynamically to assure a two-bit buffer zone of clear bits around a polygon's maximum extent. If the user selected polygon crosses one or more maps, the polygon is subdivided into several new polygons. Once the total map coverage desired has been defined, what available map sources are determined and the resulting subset is displayed, if the resulting coverage is acceptable, the user may transfer the data to the display. |
