Results
To verify the functionality of the different modules of the Shell, the simulated DVD data files were created for input in absence of actual DVD kit from SOI They were organized as per the DVD structure referring document as mentioned in Ref.2. It contains a sample map of few base categories accommodating all possible features of topographical data in DVD-1 format with associated text, not necessarily correspond to the traditional topographic map as shown in Fig.1. The above input DVD file was passed to the process. Report providing general information on DVD kit content was generated, framework was established, basic topological features were separated and were imported into Arc/Info as base coverages containing multiple themes.

The themes were extracted tile-wise; LUT was applied with codification of features as per NRIS standards. Final output representing NRIS layers of different categories were derived and verified with the sample MAP mentioned in Ref.3.

Fig.1 Input Simulated DVD data (Output Sample MAP)



Output NRIS thematic coverages (Roads, Railways, Canals)

Conclusions
This Shell will be made operational to automate generation of thematic coverages in NRIS spatial database using the SOI-DVD data on regular basis, to meet the basic requirement of the NRIS project for spatial database layers creation and updation. As a result, significant amount of digitization effort, errors and time for generation of thematic layers has been eliminated.

In future, the NRIS spatial database will be modified using temporal ISRO satellite imageries. These modified NRIS database will be taken up to generate a DVD data kit using this Shell representing up-to-date and high resolution topographic information. Thus, it provides a scope of customized up-to-date thematic maps library generation along with up-to-date DVD base maps library generation.

Using the Shell, extraction of linear features for overlaying on available Aerial or Satellite data can be made and can be useful for further detail analysis.

The development of this Shell enables compatibility of DVD format defined by Survey Of India with the commercial standard format of GIS Arc/Info. In future, the Shell can establish compatibility with other standard formats as and when need arise.

Acknowledgements
The designer and development team is thankful to Shri A.R. Dasgupta, Dy. Director SIIPA, for allowing to carry out this activity. Shri I.C. Matieda, Head GESD, Shri P.D. Yadav, Scientist GETD and Smt. Sunanda Trivedi, Scientist SIPG deserves our special thanks for providing valuable inputs and discussion support.

References
[1] Tutorial notes on Geographic Information System, GIS The Basics, April 1996

[2] National Standard Exchange Format for Digital Vector Data, Survey of India, May, 1992

[3] National (Natural) Resources Information System, Node Design and Standards, July, 1998

[4] Correspondence Scheme for Features Codification and Standardization, DVD vs. NRIS, April, 1999

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