At least half of my work week involves working with ArcGIS Server. So when my organization upgraded to ArcGIS Server 10 I was naturally curious what improvements were made to the software for map service caching purposes. The most well-known and highly publicized caching-related improvement for ArcGIS Server 10 is the compact cache, which groups individual tiles into bundle files instead of storing each tile separately. This modification not only helps shorten caching time, but it also shortens the time required to copy a cache from one location to another.
While the introduction of the compact cache option is important to know about, there are two lesser-known improvements that caught my eye which could be useful to those who regularly create or work with cached map services.
Mixed Tile Format
When configuring a map cache one needs to decide what image format to use for the cache tiles and what one decides will determine whether or not portions of a tile can be transparent. If one selects JPEG then none of the tiles, even those along the cache periphery that have large areas that should be transparent, will have transparency. This is an issue when one wants to overlay two cached images on top of one another. In ArcGIS Server 10 one can work around this by using the mixed tile format, which provides the needed transparency in periphery tiles by storing them as PNG32 and storing all other tiles as JPEG.
Export / Import Map Server Cache Tools
Two tools available in ArcToolbox in ArcGIS 10 that could be very useful to those creating or modifying cached map services are the Export Map Server Cache and Import Map Server Cache tools. The name of each tool clearly identifies each tool’s function. However, what might not be so clear is the usefulness of these tools in the caching process. Using these tools together provides the ability to collaboratively build a cache. For example, one user could export a specific portion of a map service’s cache that they updated and share the update with others who can then incorporate the update in their own versions of the same map cache by using the Import Map Cache tool. Additionally, the Export Map Cache tool can be used to export the cache to a folder that ArcGIS Desktop users can access. The ArcGIS Desktop users can pull in the cache as a raster dataset, thus eliminating the need to be connected to the ArcGIS Server that hosts the cache’s parent map service.
For more information on all improvements associated with ArcGIS Server 10, refer to ESRI’s What’s new in ArcGIS Server 10 page.