Zipf-like Distribution and Its Application to Image Data Tile Request in Digital Earth

Network geography information systems,such as digital Earth,are getting more popular and offering geography navigation services for data requests of large-scale and high intensity.Hotmap is designed for Microsoft Virtual Earth by Microsoft Research to analyze the access distribution of spatial data.For the first time,Hotmap understands the request distribution of image data as power-law.However,Hotmap does not characterize the details.Through statistical analysis of four GlobeSIGht server logs with different granularity of times,the Zipf-like distribution(one of power-law)for image tile requests is found.Image data has a heavy skewed access,which means hotspot data exist and 20%(5%)of tiles pull nearly 80%(50%)requests.This finding helps the design and optimization of digital Earth system,for example,in aspects of image data storage declusting and distributed cache.