NSDI METADATA STANDARDS
NATIONAL SPATIAL DATA EXCHANGE(NSDE) FORMAT
The Metadata standard specifies the elements needed to support establishment of a NSDI Metadata and also for major uses of metadata: (1) to maintain a catalogue of a NSDI Organisation's spatial data holdings (2) to provide information to users of the holdings and the catalog of information (3) to provide information needed to process and, investigate spatial data holdings for access by users (4) to standardize the exchange format of the spatial data. The standard defines the information required by a prospective user (1) to determine the availability of a set of spatial data, (2) to determine the compliance of a set of spatial data for an intended use, (3) to determine the means to access the set of geospatial data, and (4) to access the set of spatial data successfully.
The fundamental aspects of the NSDI Metadata will be:
- Mainly consisting of spatial data -map and image data from different NSDI agencies. This could be at different scales- 1:250K to 1:10K through 1:50k and 1:25k.
- The Metadata format will be GIS independent but will be compliant to most (if not all) GIS packages. Thus the NSDI database engine will have to be an independent one.
- Web-enabled so that on-line access on nsdi.org is possible. This will at least open up information about spatial data availability.
Realization of National Spatial Data Infrastructure(NSDI) is the current national focus. NSDI is proposed as a single window mechanism for providing access to the spatial data being generated and managed by various agencies in the country. It is visualized as a network of databases consisting of the domain specific datasets/Products created and managed by various agencies like Survey of India, Geological Survey of India and a central database having metadata to be managed by NSDI secretariat.
The format described here under, has evolved from the Digital Vector Data(DVD-3) format, which was earlier designed as the National Standard Exchange Format for Survey of India digital Cartographic vector data. This format catered for point, line and polygon topology describing relationships among spatial features. The currently proposed format has provision to include digital images acquired by satellites and Digital Elevation Model(DEM) and coded raster data. Furthermore the NSDE format also accommodates various types of thematic data sets along with the associated attribute data in tabular form.
The data in NSDE Format will be supplied to users as a set of files. When supplying the data on media all the files would be copied unlabelled in the same sequence with the End-Of-File(EOF) mark after each file and one extra EOF mark at the end of all files to indicate the end. In case the dataset cannot be accommodated in one media, the files will be copied sequentially into additional media which will be serially numbered and indicated in first file.