Use of map data difference tiles to iteratively provide map data to a client device

摘要

To provide map data for rendering map images corresponding to a selected geographic region at a client device, a map server generates a set of base map tiles having vector descriptors, each of which indicates a geometry of a respective map element, in accordance with a non-raster format for rendering a first map image. The map server, at some point, provides the base map tiles to the client device. Upon receiving an indication that a specific map image for the selected geographic region is to be rendered at the client device, the map server further generates a set of difference map tiles that indicate changes to be made to the set of base map tiles and sends the difference map tiles to the client device for use, along with the set of base map tiles, in rendering the requested specific map image.

主权项

1. A computer-implemented method for providing map data to a client device via a communication network, the method comprising:
generating one or more base map tiles, each base map tile including a plurality of vector descriptors for rendering and displaying, at the client device, a first map image for a selected geographic region, wherein the first map image corresponds to a first zoom level, wherein each vector descriptor indicates a geometry of a respective map element in accordance with a vector graphics format, including generating a set of style data defining visual characteristics to be applied to the geometry of at least some of the plurality of vector descriptors; causing the one or more base map tiles to be transmitted to the client device via the communication network; receiving an indication that a second map image for the selected geographic region is to be rendered at the client device, wherein the second map image is different from the first map image but includes a region covered by at least one of the base map tiles, and wherein the second map image corresponds to a second zoom level different than the first zoom level; generating a set of difference map tiles that define a difference between the first map image and the second map image to be displayed, including specifying map features associated with the second zoom level, the set of difference map tiles including one or more descriptors, each of which corresponds to a change in a map element as rendered in the second map image as compared to the first map image, including generating a different set of style data defining different visual characteristics to be applied to the geometry of the at least some of the plurality of vector descriptors; and causing the set of difference map tiles to be transmitted to the client device via the communication network for rendering and displaying the second map image using at least some of the information in the one or more base map tiles and the set of difference map tiles.