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IRS-1B based FCC image interpretation for land use and land cover mapping: An expert system approach
Accordingly, the knowledge base has been developed here too. Three layers of sections for each land use and land category occurring in table1 have been used. These are shown in the fig2, which represents screen shot of the section tree. The rules in each section are arranged in the first come first serve sequence that decides flow of control among the sections. The firing of a rule in any section is governed by the related parameters. All types of parameters have been used in developing knowledge base as per the design requisition. The section consult again represents end of session and can direct control, on user’s response, such that it become possible to do consultation for all land use & land cover types in sequence in each session, otherwise, it needs to start re-consultation for each type. In order to tackle the uncertainty related with any Boolean parameter (when a user responses as Unknown to a question ) multilevel dialog has been designed so that user become aware with what is being asked by the system. The top level of dialog uses standard scientific terms and on each lower level effort has been made to simplify the terms. The declaration field of each parameter contains proper explanation for HOW type explanation while the explanation field contains the explanation to the question related to parameters. Each parameter contains picture name in the picture field, which displayed during consultation. Pictures are stored in picture database in BMP format. On the picture displayed with question of parameter, the land use land cover type has been specified using hotspot editor. Current version of ESTA allows use of picture in the title, parameter, in advice and in action list. However it has been found essential in, some places, to include pictures in explanation. This has been achieved by directing control flow in the advice and pictures have been used to make easier understanding the question. Such an example is shown in fig 3 where the user selects help option. This drives the system in advice window, as shown in the screen shot of fig.4, where the user gets option to see more interpreted FCC images to develop idea about visual image interpretation. The developed knowledge base has been stored in compiled format to optimize the performance
 Fig. 4: A Screen shot in response to fig.3 Consultation and Result The consultation with the system can be initiated by loading knowledge base in memory. ESTA allows only one knowledge base at a time. As the programme runs ESTA goes in start section and looks for the rules. It asks question related to parameters in ESTA Consult window It executes rules in order of the arrangement. The parameter Land Cover places menu of all the land cover and land use types from where user can choose any one and accordingly, the control is transferred to the related section at the second level. At the second level image interpretation is done. User gets here decision of system in advice window. However, as shown in screen shot of fig. 4, the advice window has been also used to provide help on question using additional figures for aforesaid reasons. The interpretation rules in the sections, at second level, have been placed in first come first serve sequence. These sequences have been logically arranged keeping in view minimizing the situation of conflict, which is very common in image interpretation [22]. However, this does not provide strong strategy to overcome the problem of conflict resolution.  Fig. 4: Standard FCC image taken by IRS - 13 In the present work two FCC images, taken by IRS- 1D & IRS-1B satellites, of Hajipur area of district of Vaishali of Bihar have been used for the purpose of identification of the land use/land cover. The photographs shown in fig.6 and fig.7 have been taken in the Oct. 1998 by IRS-IB & in May 1999 by IRS-ID respectively, in the same spectral bands. The FCC taken by IRS-1D is based on the data collected by multispectral LISS III sensor. It is relatively high resolution image .It has been used here to see the temporal variation in the area. These two images are of same area, Vaishli district in Bihar, India, and is shown in fig 8 (from www.mapsindia.com) but are taken in different season. Thus by comparing the two images several land use/land cover showing temporal variation like permanent water logging area, temporary water logging area etc have been detected. The identified land use/ land cover areas have also been presented in fig.9.No evidence of snow and hilly area has been found. In the course of interpretation the user can learn the visual image interpretation skill by going through the rules used by the system. The result of the system is satisfactory at the macroscopic level.  Fig. 5: Standard FCC image taken by Satellite IRS - 1D Conclusion & future work It may be concluded that the knowledge acquisition, analysis and their structuring to develop knowledge-based rule is major work in this presentatation. Testing the knowledge base and do required correction is relatively smaller part of the work. The system is capable in doing classification at the first level of USGS land use & land cover classification scheme. The developed system is promising and encouraging. It helps in illustrating the major concepts of visual image interpretation and similar system development. The system can be used by the beginners to learn visual image interpretation of the FCC image. The knowledge base of the system stores rule in first come first serve sequence. This is not very strong resolution for conflicts that often arises in the FCC image interpretation. However, by assigning some priority value to each rule in compliance with the human expert’s view stronger conflict resolution can be achieved, as it is independent of ordering of rules. Also the picture base of the system is required to have more interpreted images to make the system useful for lay users. In order to make system more useful it is recommended to integrate digital techniques also. As in the coming decades the need of on screen interpretation of high-resolution satellite image is likely to increase [16], the knowledge base for high-resolution image interpretation can be developed in the same way.  Fig. 6: Location of Vaishali district in Bihar Acknowledgement This work was supported by CSIR, NewDelhi. We would also like to thanks to Bihar Remote Sensing Center Patna, for technical support and advice.  Fig. 7: Representation of identified Land use and Land covers (for fig. 4) References
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