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Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
SQL database in Microsoft Fabric
SQL Server supports extended methods on geometry instances that go beyond the Open Geospatial Consortium (OGC) standard methods. These extended methods provide additional functionality for working with planar geometric data, including Z (elevation) and M (measure) values, precise buffer operations, simplified representations, and enhanced WKT/WKB formats.
Extended methods vs. OGC methods
While OGC methods provide standardized spatial operations defined by the OpenGIS specification, extended methods offer SQL Server-specific enhancements:
- OGC methods: Standardized operations for interoperability with other geospatial systems. Use when standards compliance is required.
- Extended methods: SQL Server-specific operations that provide additional functionality, performance optimizations, or support for features not covered by OGC standards (such as circular arcs, Z/M values, and advanced buffer control).
For most spatial tasks, OGC methods provide the necessary functionality. Use extended methods when you need the extra capabilities they provide.
Enhanced representation formats
These methods provide alternative formats for representing geometry data, including support for Z (elevation) and M (measure) values.
| Method | Description |
|---|---|
| AsBinaryZM (geometry DataType) | Returns the OGC Well-Known Binary (WKB) representation augmented with Z (elevation) and M (measure) values. |
| AsTextZM (geometry Data Type) | Returns the OGC Well-Known Text (WKT) representation augmented with Z (elevation) and M (measure) values. |
| AsGml (geometry Data Type) | Returns the Geography Markup Language (GML) representation of a geometry instance. |
| ToString (geometry Data Type) | Returns the string representation of a geometry instance augmented with Z and M values. |
Z and M coordinate access
These methods access the Z (elevation) and M (measure) values of geometry instances, supporting 3D and 4D spatial data.
| Method | Description |
|---|---|
| Z (geometry Data Type) | Returns the Z (elevation) value of a geometry instance. Null if not defined. |
| M (geometry Data Type) | Returns the M (measure) value of a geometry instance. Null if not defined. |
| HasZ (geometry DataType) | Returns 1 if a geometry instance contains at least one point with a Z value. |
| HasM (geometry DataType) | Returns 1 if a geometry instance contains at least one point with an M value. |
Advanced buffer operations
These methods provide more control over buffer calculations than the standard OGC STBuffer method.
| Method | Description |
|---|---|
| BufferWithTolerance (geometry Data Type) | Returns a geometric object representing all points within a specified distance from a geometry instance, with explicit tolerance control for precision. |
| BufferWithCurves (geometry Data Type) | Returns a geometry instance representing all points within a specified distance, preserving circular arc segments in the result. |
Geometry simplification
These methods create simplified versions of geometry instances, useful for performance optimization and visualization at different scales.
| Method | Description |
|---|---|
| Reduce (geometry Data Type) | Returns a simplified approximation of a geometry instance produced by running the Douglas-Peucker algorithm with the specified tolerance. |
| CurveToLineWithTolerance (geometry Data Type) | Returns a polygonal approximation of a geometry instance containing circular arc segments, with explicit tolerance control. |
Spatial relationship queries
These methods perform advanced spatial relationship queries.
| Method | Description |
|---|---|
| ShortestLineTo (geography Data Type) | Returns a LineString instance with two points representing the shortest distance between the two geometry instances. |
Validity and type checking
These methods provide detailed validity checking and type information.
| Method | Description |
|---|---|
| IsValidDetailed (geometry DataType) | Returns a message that helps identify problems with an invalid geometry instance. |
| MakeValid (geometry Data Type) | Converts an invalid geometry instance into a valid instance with a valid OGC type. |
| InstanceOf (geometry Data Type) | Returns 1 if a geometry instance is of the specified type. |
| IsNull (geometry Data Type) | Returns 1 if a geometry instance is null. |
Spatial operations
These methods perform spatial operations with enhanced capabilities.
| Method | Description |
|---|---|
| Filter (geometry Data Type) | Offers a fast, index-only intersection method to determine if a geometry instance intersects another instance. |
Version compatibility
These methods provide information about SQL Server version compatibility.
| Method | Description |
|---|---|
| MinDbCompatibilityLevel (geometry Data Type) | Returns the minimum database compatibility level that recognizes the geometry data type. |