Spatial data types allow for location-based queries by representing geometric objects like points, lines, and polygons. SQL Server supports both flat (GEOMETRY) and round earth (GEOGRAPHY) spatial data types that adhere to Open Geospatial Consortium standards. Spatial data can be input and output in different formats and queried using spatial methods and indexed for performance with spatial indexes.

1. Spatial Support

2. Relational and Non-Relational Data Relational data uses simple data types Each type has a single value Generic operations work well with the types Relational storage/query may not be optimal for Hierarchical data Sparse, variable, property bags Some types benefit by using a custom library use extended type system (complex types, inheritance) use custom storage and non-SQL APIs use non-relational queries and indexing

3. Spatial Data Spatial data provides answers to location-based queries Which roads intersect the Microsoft campus? Does my land claim overlap yours? List all of the Italian restaurants within 5 kilometers Spatial data is part of almost every database If your database includes an address

4. Spatial Data Types The Open Geospatial Consortium defines a hierarchy of spatial data types Point Linestring Polygon MultiPoint MultiLinestring MultiPolygon GeomCollection Non-instanciable classes based on these

5. OGC Hierarchy of Spatial Types

6. SQL Server 2008 and Spatial Data SQL Server supports two spatial data types GEOMETRY - flat earth model GEOGRAPHY - round earth model Both types support all of the instanciable OGC types InstanceOf method can distinguish between them Supports two dimension data X and Y or Lat and Long members Z member - elevation (user-defined semantics) M member - measure (user-defined semantics)

7. GEOGRAPHY Requirements GEOGRAPHY type has additional requirements Coordinate order is Longitude/Latitude for WKT, WKB Latitude/Longitude for GML Exterior polygon rings must have their describing coordinates in counter-clockwise order (left-hand rule) with interior rings (holes) in clockwise-order (right-hand rule) A single GEOGRAPHY object cannot span more than a logical hemisphere

8. Spatial Data demo

9. Properties and Methods The spatial data types are exposed as SQLCLR UDTs Use '.' syntax for properties Use '.' syntax for instance methods Use '::' syntax for static methods Methods and Properties are case-sensitive Each type uses a set of properties and methods that correspond to OGC functionality With Extensions Geometry implements all OGC properties and methods Geography implements most OGC properties and methods 2-D vector only implemented

10. Input Spatial data is stored in a proprietary binary format Instance of the type can be NULL Can be input as Well Known binary - ST[Type]FromWKB Well Known text - ST[Type]FromText Geography Markup Language (GML) - GeomFromGml Can also use SQLCLR functions Parse Point - extension function Input from SQLCLR Type - SqlGeometry, SqlGeography Spatial builder API – Populate, IGeometrySink/IGeographySink

11. Output Spatial Data Can Be Output As Well Known binary - STAsBinary Well Known text - STAsText GML - AsGml Text with Z and M values - AsTextZM SQLCLR standard method ToString - returns Well Known text As SQLCLR object - SqlGeometry, SqlGeography Other useful formats are GeoRSS, KML Not Directly Supported

12. SRID Each instance of a spatial type must have an SRID Spatial Reference Identifier SRID specifies the specification used to compute it SRID 4326 - GPS, default for GEOGRAPHY SRID 4269 - usually used by ESRI SRID 0 - no special reference, default for GEOMETRY Methods that use multiple spatial types (e.g., STDistance) must have types with matching SRID Else method returns NULL Geography instance must reference one of these SRID stored in sys.spatial_reference_systems

13. Useful Methods/Properties Descriptive STArea STLength STCentroid Relation between two instances STIntersects STDistance Manipulation STUnion STSymDifference Collections STGeometryN STPointN

14. Sample Query Which roads intersect Microsoft’s main campus? SELECT * FROM roads WHERE roads.geom.STIntersects(@ms)=1

15. Extension Methods SQL Server 2008 extends OGC methods MakeValid - Converts to OGC valid instance BufferWithTolerence - similar to STBuffer, allows approximation and variation Reduce - Simplify a complex geography or geometry NumRings, RingN - polygons with multiple rings GML support Z and M properties and AsTextZM method Filter - provides a quick intersection set but with false positives EnvelopeCenter,EnvelopeAngle for Geography types

16. Spatial Indexes SQL Server Spatial Indexes Based on B-Trees Uses tessellation to tile 2D to linear Divides space into grid of cells(uses Hilbert algorithm) Meant as a first level of row elimination Can produce false positives Never false negatives You specify Bounding box of top level grid - GEOMETRY index only Cells per object - number of cells recorded for matching Grids Four Grid Levels Three Grid Densities Per Level - Low, Medium, High

17. Tessellation process

18. Spatial Analytics demo

19. Review Spatial data provides answers to location-based queries SQL Server supports two spatial data types GEOMETRY - flat earth model GEOGRAPHY - round earth model Spatial data has Useful properties and functions Library of spatial functions Three standard input and output formats Spatial indexes

20. Resources SQL Server Spatial Data Technology Center http://www.microsoft.com/sql/2008/technologies/spatial.mspx Whitepaper: Delivering Location Intelligence with Spatial Data http://www.microsoft.com/sql/techinfo/whitepapers/spatialdata.mspx MSDN Webcast: Building Spatial Applications with SQL Server 2008, Event ID: 1032353123 Whitepaper: What's New for XML in SQL Server 2008 http://www.microsoft.com/sql/techinfo/whitepapers/sql_2008_xml.mspx Whitepaper: Managing Unstructured Data with SQL Server 2008 http://www.microsoft.com/sql/techinfo/whitepapers/sql_2008_unstructured.mspx

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