Conference Proceedings: National Spatial Data Infrastructure (NSDI)

The NSDI Servers
The NSDI will be a set of GIS database servers – one NSDI Node for each participating agency. Thus, the NSDI will have Nodes for GSI for geological data; SOI for topographical data: NRSA for satellite images and thematic data; NRIS for natural resources management and development data; NBSSLUP for soil data and so on. Each NSDI agency will maintain its own Node as part of an Intranet and link to the “master” NSDI server.

The NSDI organization needs to ensure the following:

A flexibility in the design to adapt to the needs of different users.
A system of validation checks to maintain the integrity and consistency of the data elements.
A level of security for minimizing damage to the data.
Minimizing redundancy in data storage.

The NSDI design would also define a comprehensive framework of the database and allow the database to be viewed in its entirety so that interaction and linkages between elements can be pre-defined and evaluated. The design would also permit identification of potential bottlenecks and problem areas so that design alternatives can be considered. The design would also help in identification of the essential and correct data elements to be incorporated into the database and filter out irrelevant data. The specification of the NSDI database, in terms of the content, tolerances and accuracies, procedure for creation etc. This design sets out the logical structure of the database elements and is also independent of the commercial GIS packages. Hopefully, the commercial GIS packages would provide gateway solutions for interfacing their packages to NSDI Standards and NSDI would work with the GIS vendors to enable this.

It is also necessary to look into aspects of Data Warehousing and related Data Mining technologies to fully utilize the enormous amount of data that is likely to be part of the NSDI. While the granularity of the data can be quite high, the data volumes would also be very high. One could use the concepts of Data Marts and Data Warehouses.

Definition of updation procedures could also be a part of the design activity so that newer data can be incorporated in future and the database is "active".

The NSDI Gateway and Intranet
Each of the NSDI Node will be on an Intranet – ensuring full security and “closed-user” access. The NSDI nodes would be linked to the master NSDI Server – which will serve as the Gateway on the Internet for the NSDI Intranet Nodes and will host the NSDI Metadata. The NSDI Master Server will also perform the role of the NSDI Electronic Clearinghouse and will “direct” access to appropriate NSDI Nodes based on access protocols.

The NSDI Gateway would be a web domain name (maybe, www.nsdi.gov.in) with individual Nodes linked to the NSDI domain.

Traffic on the NSDI is expected to be “asynchronous” with user queries of low-density and return “service” from the Nodes to the user being high-density spatial information. The NSDI Gateway on the wide area protocol and the NSDI Intranet would require sufficient bandwidth of a communication backbone. Traffic-hits on the NSDI would grow slowly and would require design of network architecture using both terrestrial and VSAT links.

NSDI Search and Access Protocols
Support of discovery and access service for spatial information in NSDI would depend upon development of a "Search service". The search engines to look for and discover data and information could adopt the Z39.90 standard (internationally adopted by spatial data infrastructures) that allows software and system independent search. Further integration of these services with web mapping, live access to spatial information, and additional services can lead to exciting user environments in which data can be discovered, evaluated, fused, and used in problem-solving. The Catalog Gateway and its user interface allow a user to query distributed collections of spatial information through their metadata descriptions. Figure-4.4 shows the possible framework for NSDI Search and Access.

Figure 4.4 : NSDI Search and Access
A user interested in locating spatial information uses a search user interface, fills out a search form, specifying queries for data with certain properties. The search request is passed to the Catalog Gateway and poses the query of one or more registered catalog servers. Each catalog server manages a collection of metadata entries. Within the metadata entries there are instructions on how to access the spatial data being described. There are a variety of user interfaces available in this type of Catalog search in various national and regional SDIs around the world. Interoperable search across international Catalogs can be achieved through use of a common descriptive vocabulary (metadata), a common search and retrieval protocol, and a registration system for servers of metadata collections.

NSDI must adopt the web browser for display and interface of queries. NSDI mapping on the Web will include the presentation of general purpose maps to display locations and geographic backdrops, as well as more sophisticated interactive and customizable mapping tools. The intention of online or Web Mapping is to portray spatial information quickly and easily for most users, requiring only map reading skills. Web mapping services can be discovered through online directories that serve both spatial data (through metadata) and services information. In fact, web mapping services are often used to assist users in spatial search systems, showing geographic context and extent of relevant data against base map reference data.

Web based mapping would provide the functionality to NSDI to help discover and visualize spatial information referenced from Catalog Servers. A Catalog Service System is implemented through Internet-based software that allows users to inventory, advertise, and access metadata and associated spatial information within a global framework of servers and also to discover data and web mapping services and then requesting and displaying maps from different servers.

Access rules will define the restrictions and categorization of users to spatial information. In addition, the access rules could also define pricing rules and ember e-commerce protocols for users to access the NSDI nodes.

Access to NSDI spatial data from the users point of view is a part of a process of that goes from discovery to evaluation, to access and finally to exploitation. Access involves the order, packaging and delivery, offline or online, of the data (coordinate and attributes according to the form of the data) specified.

Comments : Info@GISdevelopment.net