Abstract: Display of digital maps with gradually changing perspective is provided. A perspective engine selects from among possible foreshortening ratios depending on the selected map scale. In one embodiment, the perspective engine uses a fixed perspective view corresponding to each of a fixed set of scales. In alternative embodiments, there is a continuum of scales, and parameters are specified as functions of the scale, rather than as fixed values. In general, at smaller scales—that is, more zoomed-out—the displayed perspective appears to be more flat, as though looking straight down at the map. At larger scales—more zoomed-in—the map is displayed with increasing perspective. In some embodiments, once a threshold scale is reached, continuing to zoom in does not additionally increase the perspective; similarly, once a threshold zoomed-out scale is reached, the map continues to be displayed in a two-dimensional flat appearance.

Abstract: The present invention is a global positioning system that helps a blind pedestrian navigate through a city. This system uses the Department of Defense Global Positioning System (GPS) and a Differential GPS receiver to determine a pedestrian's longitude and latitude. Once these coordinates have been determined, they are correlated with a computerized map database. The map database holds the names and coordinates of specific locations, such as intersections, in a particular region. The system of the present invention retrieves the names of locations from the map database that are near the pedestrian. These names are then output to a voice synthesizer.