ESRI uses ArcGIS Server to create and publish the maps hosted for ArcGIS Online. ArcGIS Online maps use server-side map caching, meaning that predrawn images of the map are stored on the server so that you can quickly request them through a URL. Cache services support high performance and scalability.
The tiling scheme includes the scale levels, point of origin, coordinate system, and image format of the cache tiles. These properties define where tile boundaries will exist and are important to match when overlaying caches in some clients. Other properties, such as, image format and antialiasing, are also written into the tiling scheme.
ArcGIS Server 9.3 makes it easier for you to choose to use the Google Maps/Bing Maps (formerly Microsoft Virtual Earth) or ArcGIS Online tiling scheme for your caches. These tiling schemes allow you to easily overlay your cache tiles with data from these online mapping services. ArcGIS Server 9.3 includes these tiling schemes as built-in options when loading a tiling scheme.
NOTE: At this time, there are no online maps hosted by ESRI that use the new ArcGIS Online/Bing Maps/Google Maps tiling scheme available in ArcGIS Server 10.
The Google Maps/Bing Maps tiling scheme uses 256 x 256 pixel tiles. With this tiling scheme, the data frame of your source map document must use the Web Mercator Auxiliary Sphere coordinate system. This tiling scheme is ideal if you'll be overlaying your maps with Bing Maps or Google Maps or with other ArcGIS Online maps in the Google Maps/Bing Maps tiling scheme. Another advantage of this tiling scheme is that it is widely known in the Web mapping world, so the tiles will match those of other organizations who have used this tiling scheme.
All new online maps from ESRI use the Google Maps/Bing Maps tiling scheme. For common attributes for ArcGIS Online maps in the Google Maps/Bing Maps tiling scheme, see Common attributes for maps using the Google Maps/Bing Maps tiling scheme.
For more information on the Google Maps/Bing Maps tiling scheme, see Designing a map to overlay ArcGIS Online in the ArcGIS Server .NET or Java Help.
The ArcGIS Online tiling scheme uses 512 x 512 pixel tiles. With this tiling scheme, the data frame of your source map document must use the WGS 1984 geographic coordinate system. The ArcGIS Online tiling scheme yields the best performance and quality when creating 3D globe caches from 2D map cache tiles. The ArcGIS Online tiling scheme tends to create smaller caches than the Google Maps/Bing Maps tiling scheme, because the larger tile dimensions produce fewer files.
Many older ArcGIS Online maps use the ArcGIS Online tiling scheme; however, the content in these maps is no longer updated. For common attributes for these services, see Common attributes for maps using the ArcGIS Online tiling scheme.
For more information on the ArcGIS Online tiling scheme, see Designing a map to overlay ArcGIS Online in the ArcGIS Server .NET or Java Help.
If you have been using maps in the the ArcGIS Online tiling scheme and want to migrate them to the Google Maps/Bing Maps tiling scheme, see Migrating map tiling schemes.
See The tiling scheme section in the Choosing Cache Properties topic in ArcGIS Server 9.3 .NET Help for more information on the Google Maps/Bing Maps tiling scheme and the ArcGIS Online tiling scheme.
See also "Reusing ArcGIS Online tile caches "