How Spectrum Spatial Analyst Renders Maps

For backgrounds maps, Spectrum Spatial Analyst uses the Map Tiling Service or a third-party source such as Bing or OpenStreetMap (OSM). It returns 256 x 256 pixel map tiles and caches the tiles on the server for optimal performance.

For business maps (uploaded by customers and shown in the legend) Spectrum Spatial Analyst renders data live and makes a series of 542 x 542 pixel map image requests for each map in the legend. For example, there are two maps, and each map has two layers (image below). A map group relates to one Named Map loaded into Spectrum Spatial.

Figure 1: Map Legend

Map images are placed adjacent to each other on the map window to complete the whole map. The images are placed overlapping by 15 pixels to ensure map symbols do not appear cropped at the edges. Below we see that six map requests are needed to fully cover the map window, which results in a total of 12 map requests (six for “Conservation Map” and another six for “Spaces and Trees Map”).

Figure 2: Map Images

When a map image returns to Spectrum Spatial Analyst, it is cached locally in the user's browser for 60 minutes. Spectrum Spatial Analyst uses the cached map image when the user pans and zooms the map.