NRIS is oriented towards providing information for decision makers and encompasses information on natural resources related to land, water, forest, minerals, soil, ocean etc. and socio-economic information such as demographic data, amenities, infrastructure etc. The integration of these sets of data would aid the decision making process for systematic resource utilization Thus NRIS is visualized as a network of GIS based nodes covering the districts and states and the entire country
The NRIS nodes are configured with huge volume of spatial and non-spatial data generated at various work centres by different set of people. Moreover, these databases have to be accessed through a set of query and decision support shells, which are user friendly and provide transparent access. As these shells are also developed by different work centres, the uniformity and validity of the databases against laid down NRIS standards is of uproots importance.
For maintaining the uniformity NRIS standards have been laid out which spells out node database contents along with associated coding scheme for each element and structure of database organization including the spatial framework and schemes for linking spatial and non spatial elements in the database.
Furthermore an approach and S/W module has also been developed and implemented for maintaining the integrity of database contents vis a vis feature codification scheme referring to master templates.
Software Requirements Currently NRIS databases are created using UNIX based ARC/INFO GIS software. So this module has been developed using ARC Macro Language (AML).
Methodology
The module refers to a pre-created checklist of all the database elements, which should exist in a typical NRIS node. The checklist contains
- the name of spatial layers (as per NRIS convention)
- type of spatial feature (poly, line, point)
- the name of attribute table containing the attribute descriptors for spatial features
- The name of the key field which links the spatial layer and attribute table.
- Database definition of the key field as per NRIS standard
- Range of values of key field, allowed , as per NRIS standards
- List of columns in attribute table which contain the description for spatial features (designated as per NRIS standards)
The validation module loops through this checklist and performs detailed validation checks as described below.
The first step in validation is the check on existence of the data elements. After ascertaining the existence of spatial and attribute components of the desired data element, the module proceeds further for verifying the correctness of data element from three considerations viz. a) spatial fidelity of the data element as a correct GIS layer. b) Spatial fidelity of the layer against laid down spatial framework under NRIS. c) Correctness of the feature codification as against laid down NRIS standards.
Checking the spatial fidelity against GIS conventions
Module checks for the correctness of topology of spatial data elements. Depending upon the type of feature specified in checklist, i.e. polygon, line, point, the checks are performed on whether,
- layer is free of label errors
- whether requisite topology exists or not
Spatial fidelity against laid down spatial framework under NRIS. Under this section, checks are made on projection/co-ordinate system used; adoption of scheme for identifications of registration points, spatial extend of the data elements and whether the tolerances are as per specified standards.