For these characteristics of large landscape image such as huge saving memory and limited basic graph units to compose image

in this paper

a method based on multi level database was advanced to reduce the memory of large image. The database included two parts: graph database and mapping database. The organization mode of graph database and mapping database was presented

the mapping relation between graph units and geography position in image was put forward

the extraction of graph units from multi-level database was established. The mapping database was consisted with three level data table:the base function graph table

the function unit table

image table. The based function graph which was contructed by graph units

the function unit table which was recorded the relationship of the base function graphs described a part image

the image table was contented with all function graphs with variable situation. The reflection that established the relationship of two different data tables was described by palette

this reflection was unique. One point of high class level table reflected a unit of lower level table

by this way

it would be reduced the saving memory largely. This kind of multi level database had some characteristics such as high speed and accuracy locating

less memory of large image. By this way

1G bytes image used memory less than 3M bytes.