Tile Mesh Codes Tiling Rules

8-10 Oracle Fusion Middleware Users Guide for Oracle MapViewer Figure 8–5 Tiling with a LongitudeLatitude Coordinate System On each zoom level, the map tiles are created by equally dividing the whole map coordinate system along the two dimensions X and Y, which in Figure 8–5 represent latitude and longitude. The map tile server needs this dimensional information of the map coordinate system in order to create map image tiles, and therefore you must include this information in the map tile layer configuration settings. The whole map coordinate system can be represented by a rectangle, and its boundary is specified by Xmin, Ymin and Xmax, Ymax, where Xmin is the minimum X value allowed in the coordinate system, Ymin is the minimum Y value allowed, Xmax is the maximum X value allowed and Ymax is the maximum Y value allowed. In Figure 8–5 , Xmin is –180, Ymin is –90, Xmax is 180, and Ymax is 90. You must also specify the spatial referencing ID SRID of the coordinate system to enable the map tile server to calculate map scales.

8.2.1.4 Tile Mesh Codes

Each map tile is specified by a mesh code, which is defined as a pair of integers Mx, My, where Mx specifies the X dimension index of the tile and My specifies the Y dimension index of the tile. If the tile is the ith tile on X dimension starting from Xmin, then Mx should be i-1. If the tile is the jth tile on Y dimension starting from Ymin, then My should be j-1. Figure 8–6 shows the mesh codes of the tiles on a map. Oracle Maps 8-11 Figure 8–6 Tile Mesh Codes The JavaScript map client automatically calculates which tiles it needs for displaying the map in the Web browser, and it sends requests with the mesh codes to the server. Mesh codes are transparent to the application, and application developers do not need to deal with mesh codes directly.

8.2.1.5 Tiling Rules

You must create tiling rules that determine how the map is divided and how tiles are created. The map tile server uses these tiling rules to divide the map into small map image tiles that are stored in the tile storage system. These rules are also used by the JavaScript map client. Because all tiles on a given zoom level are the same size, the map tile server needs to know the following information to perform the tile division: ■ The map tile image size width and height, specified in screen pixels. This is the physical size of the tile images. ■ The tile size specified according to the map coordinate system. For example, if the map uses a geodetic coordinate system, the tile width and height should be defined in degrees. The size can be specified either explicitly by tile width and height or implicitly by map scale. Map scale, combined with tile image size, can be used to derive the tile width and height according to the map coordinate system. The preceding information constitutes the tiling rule for a given zoom level. Each zoom level must have its own tiling rule. You must define the tiling rules when you specify the configuration settings for the map tile server, as described in Section 8.2.2 .

8.2.2 Map Tile Server Configuration