In this article we give a close look at spatial data types supported by SQL Server and the differences between them.
Apart from storing data in the form of databases, for commercial enterprises, SQL Server also supports spatial data, and can be used by organizations dealing with spatial data. Spatial Data mainly includes data related to space, in SQL Server, two different types of spatial data are supported – Geometry and Geography. Geometry mainly includes data about flat – Earth (it supports planar or Euclidean data). Geography mainly includes data about round – Earth (it supports ellipsoidal data like latitude and longitude). The spatial data supported by SQL Server, further includes 16 different data objects, also called instance types, out of which only 11 are instantiable. Meaning, they can be used for working with databases.
Categories of Geometry and Geography Data supported by SQL Server
These instances are broadly categorized under different parent categories, which determine the properties of these instances. These categories are:
Differences between Types of Spatial Data in SQL Server
The key differences between Geography and Geometry data in SQL Server are:
- Defining Connecting Edges – Data that falls under Polygon and LineString category is defined by vertices. In Geometry, connecting edges between vertices are marked by a straight line. Whereas, in Geography, connecting edges between vertices is marked by an elliptic arc.
- Defining Circular Arc Segments – Geometry uses XY Cartesian Coordinate pane for measuring circular arc segments. Geography makes use of curve segments over a reference sphere.
- Measuring Data – Measurement of distances in Geometry or flat – Earth system are provided in the same unit of measurement as the coordinates. Whereas, in Geography or round – Earth system, coordinates in the form of degrees are given for latitude and longitude, whereas meters and square meters are used for measuring lengths and areas.
- Orientation of Data – In Geometry the ring orientation of a polygon done not mean much, but in Geography, a polygon loses its value and becomes ambiguous without orientation. For instance, the differentiation between a northern or a southern hemisphere will not be clear without a ring orientation. Whenever using Geography data type for storing a spatial instance, the specification of the ring orientation and accuracy opt instance location is mandatory.
- Importance of Outer and Inner Rings – These are not important in Geography but do hold importance in Geometry.
From Research Agencies to Space Exploration – Spatial Data Support Extends the use of SQL Server Database
SQL Server has largely been used for storing typical business data, but the application has a lot more potential than just being used for storing lengthy and heavy database tables. With the support for spatial data storage, SQL Server has added on a lot to its importance and usage. Till now it was only being used a software for commercial enterprise but it can also be used by institutions making spatial discoveries, government agencies and specialized organizations who need software to manage and store spatial data. However SQL Server data files are open to incidents of data corruption and any company dealing with valuable data needs to keep a repair SQL Server software around to deal with emergencies.
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