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Ensuring the Integrity and Validity of NRIS Databases
Bharat Vaishnav,
Ketki Kharod, P.D.Yadav, R.K.Goel
Geomatics Technology Division Space
Applications Centre Ahmedabad 380 053
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
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