Digital maps are available on a large range of devices, many of them mobile. Because of the size of map data, they are often stored on a central server. Mobile devices have limited network bandwidth, and the traffic costs may be high. Local caching is a way to reduce the amount of data transmitted between the server and the client.
This thesis presents some theory related to digital map systems and caching in general and discusses some issues specific for caching spatial data. A prototype implementation of a spatial cache is used to study the effects of cache size and tile size on the performance of the cache.
The results are not as significant as expected. This is assumed to be because the usage pattern in the tests is random and an efficient cache implementation depends on predictability in the usage pattern. However, the results indicate that careful selection of tile size is important to maximize the performance of the cache.