In order to make image interpretation more accurate

efficient and flexible

and to enable remote sensing more useful in updateing some of data sets in GIS

an Interactive Image Interpretation System （I 3S）has been developed in Windows NT and VC ++ 6.0 environment since 1998. I 3S

in fact

is a raster-based system with a structure of toolbox and friendly interfaces. Through an interactive way

the system integrates the advantages of computers and human brain

functions of image processing system and GIS

experience of visual image interpretation and knowledge of geosciences together. The system

in general

can be operated in three modes:module application

single system application and multi￣system application. The first mode means one of the modules in the system is used for solving some of problems in an image interpretation process

such as registration of image and corresponding map

etc. In the second mode

I 3S is applied to image interpretation with small or medium scale through the combination of some function modules of the system. The last one is the mode for the task with large scale through networking and operating of multiple I 3S together. The module functions of the system can be divided into two categories:support module and interpretation module functions. The former consist of those functions to support system operation in normal. The functions are data input and output

registration of images and maps

image enhancement and data fusion

image filtering

extraction of double edges

RGB-IHS transformation

color exchange

data conversion from vector to raster or reverse

and interface to network

etc. The latter includes the modules to support image interpretation or classification directly

which are map layer manager

classification manager

image browser

tools of manual interpretation （such as pan brush

semi-automatically or automatically edge tracking

attribute assignment

rubber

etc.）and post-processing of classification

statistical result generation

graphic editing in raster or vector format

etc. In the system application mode

the different combinations of the function modules can flexibly formulate a series of system functions for image interpretation. They are as follows:interactive visual interpretation

supervised classification

image-segmented classification

ancillary band-added classification

dynamic change interpretation and human-machine mixed interpretation. Therefore

I 3S gives interpretation experts more space to play their leading roles in image interpretation. The principle

architectures

functions and characteristics of the system are presented in the paper.