Spatial Index is one of the key techniques that play an important role in spatial database and GIS. Currently

with the quick price reduction of computer main memory

It is possible to develop main memory spatial database. Main memory spatial database needs its own spatial indices. Two kinds of main memory oriented spatial indices have been put forward in this paper

the basic ideas of which can be traced back to disk oriented spatial index. These two main memory spatial indices are main memory grid index and main memory fieldtree index. Chomparison of these two spatial indices has been made. Test results show that in most case the main memory fieldtree index gives better performance over the grid index.