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International | Geographic Information Infrastructure
Integration of Topographic Digital Vector Data into National (Natural) Resources Information System Database Methodology Various steps are to perform for integration of SOI-DVD data into NRIS spatial database. The Shell comprises set of software modules to perform their functionality mentioned in Fig.1. The DVD data from the digital media kit following Standard Exchange Format supplied by Survey of India is downloaded into the hard disk workspace. A report file is generated to provide detailed information on the DVD kit contents for user reference. For creating a framework corresponding to the base map downloaded, necessary information related to tic, projection and boundbox are extracted from header files. Further, the DVD data is separated into point, line and polygon features as per the DVD feature codification scheme to meet requirements of NRIS spatial database. ARC/INFO provides mechanism to create ARC/INFO coverages from raw coordinates. Relevant files are created in acceptable generate format of Arc/Info and converted into point, line and polygon as the base coverage. These base coverages contain multiple themes; e.g. A line coverage may contain rail, road and drainage themes. The individual theme is extracted applying DVD vs. NRIS correspondence and the codification of features is done as per NRIS standards. SOI-DVD data is toposheet wise. Each of these is considered as a tile. These tiles have to be merged into a single coverage to get full study area extent. For these joining of the adjacent coverage is done. ARC/Info provides tool for edge-match process wherein border coordinates between adjacent coverages are matched. Thus the boundary features match across border and that map sheet corners match. Then adjacent coverages are appended depending on number of tiles the layer has. Thus the tiled data after mosaicing gives the full coverage of area of interest. Option for display and hardcopy are provided to visualize the thematic layers information fully and tile-wise. 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) 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
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