S.A.Shah, B.G.Vaishnav, Ketki Kharod, R.K.Goel
Geomatics Technologies Division, Signal, Image Information Processing Area
Space Applications Centre, Ahmedabad
Department of Space (DOS), Government of India has taken up, a major programme on realization of the National (Natural) Resources Information System (NRIS) catering to the natural resources development planning needs of the planners and decision makers at a district, state and center. The NRIS is visualized as a nationwide network of Spatial Information System nodes inter linked with each other under a Center-State-District hierarchy. Each of the NRIS nodes is built around a Geographical Information System (GIS) core and includes an integrated database known as NRIS database. This NRIS database consists of data elements in both spatial and non-spatial form on natural resources, infrastructure and socioeconomic aspects. Realization of such an integrated system will aid for monitoring, analyzing, planning and decision making on any query using available spatial information with association of non-spatial information, i.e. NRIS database. For such systematic resources utilization and conservation plan under NRIS, the basic and important requirement is to establish a methodology for easy, accurate database creation and timely updation under the NRIS standards and its environment. In the context of accommodating variety of input sources, like remote sensing data, conventional maps and data on socioeconomic and infrastructure aspects mentioned in Ref. 1, certain techniques in the form of software interface (Shells) are to be designed and implemented so that the NRIS database can be managed easily, accurately and automatically towards effective operationalization of NRIS database creation, updation and maintenance activity. Topographic information from Survey Of India (SOI) is one of the standard and reliable source for developing spatial database to meet NRIS project requirement. Recently, SOI has started making base maps in formation on topographic maps available in specific standard exchange format in digital form known as Digital Vector Data (DVD) format. Thus, there is a need to have this digital vector form data from SOI for nationwide base maps/Color separate information in 1:50000 scale covering about 5084 toposheets. On comparative study of design elements between NRIS database and SOI-DVD data, it is found that about 20% of total NRIS database elements can be prepared as base layers. It includes roads, railways, drainage, administrative boundaries, contours, elevation points etc.
This software interface (Shell) is primarily designed to eliminate huge manual effort required for digitizing about 5084 topographic maps and corresponding digitization errors. This also automates process of generating thematic information in NRIS database as per NRIS standards. Thus the Shell is designed to integrate these relevant base maps information from different categories available in DVD formats.
The software Shell comprises of procedures for look up table generation between DVD elements and NRIS elements, importing DVD data base category wise and extraction of topological data, generation of thematic coverages, integration to mappable workspace, mosaicing them with area of interest and their visualization. It is also planned to extend this Shell for maintaining up-to-date databases both for NRIS and DVD in their respective standards and formats. The spatial data of different scales and projections are also planned to be handled. To accommodate and automate the said functionality under a software package as a Shell, such process is termed as DVD data integration with NRIS database.
A comparative study has been made between the NRIS spatial database and the DVD data for their standards, structures, file formats, base categories, associated features codification scheme etc., and mentioned in Ref.2 & Ref.3. Thus, a Look Up Table (LUT) is generated by establishing relational linkage between the features of DVD data and NRIS themes mentioned in Ref.4.
This Shell is developed to retrieve the topographic data distributed in various categories provided in respective DVD formats and imports the various features available to meet NRIS project requirement into NRIS spatial database. Finally, the Shell generates the thematic layers information as per NRIS standards e.g. Wells, Drainage, Canals, Settlements, Roads, Railways, Contours, Elevation points, Villages, Talukas Districts, States and Forests Boundaries, etc. This software interface is also planned to extend its capability to generate up-to-date, high resolution topographical DVD data kit in its customized format from latest NRIS databases information, containing modified topographical features using temporal satellite data. The user interface is user friendly, provides point and click operation.
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)
Output NRIS thematic coverages (Roads, Railways, Canals)
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.
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.
 Tutorial notes on Geographic Information System, GIS The Basics, April 1996
 National Standard Exchange Format for Digital Vector Data, Survey of India, May, 1992
 National (Natural) Resources Information System, Node Design and Standards, July, 1998
 Correspondence Scheme for Features Codification and Standardization, DVD vs. NRIS, April, 1999