Data Resources for GIS – Spatial Data, Attribute Data
GIS Systems Employ a Wide Range of Data Sources. There is tremendous range in the types of data used for GIS analysis. This reflects the varied goals of the systems themselves. Since GIS may be used for applications as varied as archeological analysis, marketing research, and urban planning, the source materials can be difficult to catalog and classify comprehensively. Even within a single GIS project, the range of materials employed can be daunting.
Although the type of materials will vary greatly from project to project, GIS practitioners should be aware of some of the most commonly available data sources. These are materials collected and published by a number of government agencies and commercial businesses and are used quite widely. Even if these sources fall outside the scope of your project, it is worth learning a bit about their characteristics and limitations.
Not so long ago, most GIS projects had to rely almost exclusively upon data available only in printed or "paper" form. Much of the data available for use is still published on paper, but a great deal of information is now distributed in digital formats. The ever increasing pace of this transformation from paper to digital sources has many repercussions for GIS. Data already produced in digital format will certainly ease the work and speed the process of developing GIS, but only if users learn how to employ these new sources effectively.
The digital data revolution also means that users must often search for materials in different places. To acquire some digital sources, users must contact the producers directly and work closely with them to gain the necessary data in a useable format. Also, the Internet and Worldwide Web are being used to distribute data to a greater extent, and this means knowing where to look and how to search the networks.
Finally, all data sources have strengths and limitations. Digital sources are no different. It is important to understand their characteristics, costs, and benefits before using them. Learning a little about commonly employed digital formats will save much work in the long run.
A very good source for spatial data is the Arizona State University Libraries website at http://www.asu.edu/lib/hayden/govdocs/maps/gisdata.htm. This is a selected list of datasets and internet sources for spatial data. The site contains links to reliable sources of commonly-sought data, most of which is available free of charge, suitable for use with geographic information systems. The Map Collection at the Library Catalog portal contains spatial data available for the whole World. Most of the datasets in the Collection are available on CD-ROMs. Vector spatial data in various formats is available through different sources and providers in various formats as shown in the table below:
Local, state, and central government agencies are major sources of GIS data. A good deal of detective work is sometimes required, however, to find the data you need. This is perhaps less the case at the central level if only because certain key agencies such as the Census Department, Geological Survey of India, Central Groundwater Board, Soil Conservation Department etc, provide standard sorts of information for the entire nation.
A good place to start is the NSDI website at http://gisserver.nic.in/nsdiportal/gotogos.jsp where one can find all participating organizations listed and links to data on their websites.
The Internet and Worldwide Web: Over the past ten years the internet and web have become the leading means of acquiring primary and secondary data. In some cases, you must still contact providers in person or by mail to obtain data, but this is changing very rapidly. This now the primary means of disseminating data produced by government agencies and is assuming that role for most state governments. At the moment, finding exactly what you are looking for on the Internet can be difficult, but navigation and focused searching of the networks are becoming easier.
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Department of Geology
Aligarh Muslim University, Aligarh - 202 002 (India)