What Are Spatial Databases?
Spatial databases are databases that store spatial data or, in other words, data related to spaces in the physical world, parts of living organisms, engineering design and many other spaces of interest. The data in a spatial database is often captured, initially, in the form of digital images, so spatial databases are sometimes called pictorial or image databases.
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Spatial versus Non-spatial Data
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A spatial database is, first and foremost, a database. In other words, a spatial database is equally capable of modeling, storing and querying standard non-spatial, or alphanumeric, data as it is spatial data. In practice, spatial data is always connected to non-spatial data, so a database that handled only specific, spatial data types would be insufficient to model the data correctly.
Spatial Data Types
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Spatial databases include a set of spatial data types, such as POINT, LINE and REGION, to model geometric entities in space, and a set of special operations, such as INSIDE, INTERSECTION and DISTANCE, to define the relationships between them. The exact types and operations depend on the nature of the data -- two-dimensional or three-dimensional -- stored in the database. These types and operations may form part of a database query language, such as SQL, so that the spatial data can be queried. Extending existing database management systems by introducing spatial data types and extending SQL in an ad hoc way was the main issue with early spatial databases. Spatial data types are still not always fully understood.
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Spatial Indexing
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A spatial database must typically handle large collections of geometric objects, such as hundreds of thousands or millions of polygons. In particular, a spatial database must be able to retrieve a selection of objects, without scanning every object in the database. This means that spatial databases must use spatial indexing -- a numbering system used to select elements from a list -- and employ an efficient mathematical formula, or algorithm, for connecting, or joining, spatial objects from different classes together.
Applications
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The main application of spatial databases is in systems for storing, editing and displaying geographical information on a computer, known as geographical information systems (GIS). Spatial database applications are typically concerned with representing distinct, geometric objects arranged in space, or every point in a particular space. The first type of application allows geographers to model cities, forests and rivers, while the second allows them to model land use or the division of a country into states, provinces and districts.
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References
- Photo Credit Jupiterimages/Photos.com/Getty Images
