Spatial and Geographical data

Spatial data support in database is important for efficiently storing, indexing and querying of data on the basis of spatial location. For example, suppose that we want to store a set of polygons in a database and to query the database to find all polygons that intersect a given polygon. We cannot use standard index structures, such as B-trees or hash indices, to answer such a query efficiently. Efficient processing of the above query would require special-purpose index structures, such as R-trees for the task.

Two types of Spatial data are particularly important:

Computer-aided-design (CAD)data, which include spatial information about how objects-such as building, cars, or aircraft-are constructed. Other important example of computer-aided-design databases are integrated-circuit and electronic-device layouts.

CAD systems traditionally stored data in memory during editing or other processing, and wrote the data back to a file at the end of a session of editing. The drawbacks of such a schema include cost(programming complexity, as well as time cost) of transforming data from one form to anther, and the need to read in an entire file even if only parts of it are required. For large design of an entire airplane, it may be impossible to hold the complete design in memory. Designers of object oriented database were motivated in large part by the database requirements of CAD systems. Object-oriented database represent components of design as objects, and the connections between the objects indicate how the design is structure.

Geographic data such as road maps, land-usage maps, topographic elevation maps, political maps showing boundaries, land-ownership maps, and so on. Geographical information system are special purpose databases for storing geographical data. Geographical data are differ from design data in certain ways. Maps and satellite images are typical examples of geographic data. Maps may provide not only location information associated with locations such as elevations. Soil type, land type and annual rainfall.



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