Query efficiency of polygon objects based on the tile granularity of quad-tree

Quad-tree index has been widely used in geo-spatial database management and GIS. Yet, how to determine a suitable index depth of quad-tree for an optimal query in terms of query speed remains a difficult task. Bearing this task in mind, the authors analyze the close correlation between the index depth and the index range. The query efficiency of quad-tree is introduced as a quantitative measure which depends on the index depth and the tile granularity. By means of a test on a large number of polygon objects, the feasibility and validity of query efficiency has been proved. This research finding is, in essence, a meaningful refinement of quad-tree applications in mass geo-data.