Conference Proceedings: National Spatial Data Infrastructure (NSDI)

NSDI – Design Elements
The NSDI elements, as illustrated in Figure-4.3, would be:

Figure 4.3 : Components of NSDI

A NSDI Standard – defined and agreed to national agencies and defining content and schemas, design and process, network protocols, exchange and transfer. Standards are the crux of the NSDI and would be of relevance to database standardization - formats, exchange and interoperability; Networks-gateways and protocols; communication equipment, software standards, etc. Standards enable applications and technology to work together. Tools, applications, and data affect each other, and processes for developing standards must consider these interactions.
A NSDI Metadata of the NSDI content and information availability. The NSDI Metadata would get evolved from the NSDI Standard and as digital spatial information is populated. As a part of NSDI, one of the critical steps would be the development of a metadata standard and development metadata files.
NSDI Nodes and GIS servers of the actual spatial information – in conformity of the NSDI Standard. The NSDI Nodes would be mainly GIS based spatial databases and development oriented information systems servers - all integrated and linked to basic spatial/geographic units. The value of NSDI would be to aid as a decision-making tool and more in the context of assisting planning for developmental activities.
NSDI Search and Access Protocols that would enable search and location of spatial information. The protocols would provide the gateway for users to access NSDI. The basic issue in the operation of the NSDI is the backbone on which the information travels from one point to another. The backbone carrier will be high-speed carrier capable of providing bandwidth on demand to intermediate levels of the NSDI and to users of the NSDI.
NSDI Electronic Clearinghouse. The NSDI Clearinghouse would be the mechanism to provide access to the metadata and finally to the actual data sets. The clearinghouse has to have systems to authenticate data requests and requests spatial data volumes are usually large and download through networks may not be feasible. In such cases, the system should be able to generate media bearing the requested data for transmission by mail. The clearinghouse should also store information about the applications and availability of application specific modules that could be reused by other users. The clearinghouse would use the NSDI Search and access Protocols engines to look for and discover data and information.
NSDI User Interface that would be the front-end interface for user queries and access of spatial information. With regard to design of NSDI much depends upon the level of penetration and upper-end level of applications and services available on it. For a completely ubiquitous NSDI, the penetration will have to reach public domain and the capabilities will include online access of information applications.
NSDI Outreach and Awareness programme so as to increase the public and professional use of NSDI services and encourage e-governance concepts.

The NSDI will open up tremendous opportunities for development of Application Shells using NSDI data and will be a major value-addition activity – which though not visualized as part of NSDI is the “ultimate” goal of the NSDI. It is envisaged that a separate activity of value-added services would emerge with private sector having tremendous opportunities to contribute to this. These modules would use region specific models to generate scenarios for decision support. These models would, hopefully, cater to all clients who could range from government functionaries to individuals.

The NSDI Standard
The NSDI requires a major effort at standardizing content and schemas, design and process, network protocols, exchange and transfer. The standardization has enabled “user transparency” to information access. The NSDI Standards will evolve and grow as more and more agencies commit and access the NSDI Nodes.

The definition of the spatial framework will be very crucial in the NSDI Standard and it is important that this be decided upon in the beginning. In its simplest form, it is a frame of latitudes and longitudes with intermediate tic marks aimed at providing an invariant reference for all spatial data sets. However, most users need some basic references. Thus, it also can include ortho-rectified imagery, elevation, bathymetry, geodetic control, transportation, administrative boundaries, etc. All data has to be registered to this framework so that they can be related to each other. The framework must meet the mapping accuracy desired by the applications. The choice of the geoid and the projection systems has a bearing on the accuracy. Further, the accuracy is also a function of the scale of mapping. In India, we have the advantage of having an excellent cartographic database in the Survey of India topographic sheets. These are based on the Everest spheroid and Polyconic and Lambert Conformal Conical projections. The framework of this system is ideally suited for providing the structure for a spatial database. In addition, the large-scale databases at 1:10,000 or larger scales will be on a cadastral map base – which uses using local projections. Interlinkage of these maps with the spatial framework is an involved task and no standardized procedures exist. With the increased use of Remote Sensing for thematic mapping, such inter-linkages are essential and hence this is an area in need of urgent attention.
The NSDI Standard would have to be developed and should cover:

Content standardization – the layers, attributes and schemas that will populate a NSDI Node.
- Each NSDI-Node agency will have to develop its own thematic content standard – GSI for geology maps; FSI for forest maps; NRSA for satellite images and thematic maps; SOI for topographical maps and so on.
Design and Process standardization – the GIS database design encompassing issues of coordinate systems, projections, accuracies of databases, attribute schema forms etc. Further the database creation process standardization – the process and mechanics of actual database creation through manual digitization, scanning, keyboard entry of attributes and attribute file assimilation will also have to be developed.
Network Protocols Standards – for linking the NSDI Node servers and their inter-server communications.
Exchange and Transfer Standard – file formats for the exchange of spatial information from and to NSDI Nodes and defining output formats for user access.
NSDI Quality Standards – the quality evaluation parameters and procedures for verification and quality certification of the NSDI content.

In India, we have two standards: the NRIS Standards and the SOI DVD standard. The former is a content-based specification while the latter addresses the data exchange issues. An attempt has been made to merge the two to form a single content cum transfer specification. These are the first steps in the direction of evolving a national standard for India.

NSDI will work with different agencies, national and international, towards establishing systematic procedures that will enable each agency to undertake standard quality audits on their spatial data. Each committing agency must declare a “Quality Certification” of their spatial data and may adopt a self-certification and quality-audit process according to the NSDI-Quality Standards. It is only after certification and audit reports are made available that the spatial data form a part of NSDI.

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