Geospatial functions

At the core of Geospatial Analytics are the scalar functions and table functions provided as part of Db2® for i.

The implementation of these geospatial functions follows the OGC Simple Features for SQL specification and parts of the ISO SQL/MM Part 3: Spatial standard.

The geospatial functions fall into the following categories:

Construction of geometries from data exchange formats or coordinate data
Conversion of a geometry into a data exchange format
Comparison of geometries and discovery of relations between geometries
Construction of new geometries from existing geometries
Information about geometries
Creation of geohashes

Construction of geometries from data exchange formats or coordinate data

The following scalar functions create a geometry of the ST_GEOMETRY type or one of its subtypes from coordinate data, or from a well-known text (WKT), or a well-known binary (WKB) data exchange format:

Table 1. Geospatial scalar functions that construct geometries from data exchange formats or coordinate data
Function Use	Function Name
Construct any geometry from a WKT, WKB	ST_GEOMETRY scalar function
Construct any geometry from a WKT object	ST_WKTTOSQL scalar function
Construct any geometry from a WKB object	ST_WKBTOSQL scalar function
Construct a specific geometry from a WKT or WKB	ST_GEOMCOLLECTION scalar function ST_LINESTRING scalar function ST_MULTILINESTRING scalar function ST_MULTIPOINT scalar function ST_MULTIPOLYGON scalar function ST_POINT scalar function ST_POLYGON scalar function
Construct a specific geometry from coordinates	ST_POINT scalar function

Conversion of a geometry to a different geometry type

The following scalar functions convert one geometry type to a different geometry type:

Table 2. Geospatial scalar functions that convert one geometry type to a different geometry type
Function Use	Function Name
Convert a geometry into a linestring geometry	ST_TOLINESTRING scalar function
Convert a geometry into a multiline geometry	ST_TOMULTILINE scalar function
Convert a geometry into a multipoint geometry	ST_TOMULTIPOINT scalar function
Convert a geometry into a multipolygon geometry	ST_TOMULTIPOLYGON scalar function
Convert a geometry into a point geometry	ST_TOPOINT scalar function
Convert a geometry into a polygon geometry	ST_TOPOLYGON scalar function

Conversion of a geometry into a data exchange format

The following scalar functions convert a geometry of the ST_GEOMETRY type or one of its subtypes into a data exchange format:

Table 3. Geospatial scalar functions that convert a geometry of the ST_GEOMETRY type or one of its subtypes into a data exchange format
Function Use	Function Name
Convert a geometry into a WKT object	ST_ASTEXT scalar function
Convert a geometry into a WKB object	ST_ASBINARY scalar function

Comparison of geometries and discovery of relations between geometries

These geospatial scalar functions return information that is the result of a comparison between geometries. They return information about ways in which geographic features relate to one another or compare with one another.

Table 4. Geospatial scalar functions that compare geometries and find relations between geometries
Function Use	Function Name
Check whether two items geometries are identical	ST_EQUALS scalar function
Determine the distance between geometries	ST_DISTANCE scalar function
Determine whether geometries intersect	ST_CROSSES scalar function ST_DISJOINT scalar function ST_INTERSECTS scalar function ST_OVERLAPS scalar function ST_TOUCHES scalar function
Determine whether a geometry contains another one	ST_CONTAINS scalar function ST_COVERS scalar function ST_WITHIN scalar function

Construction of new geometries from existing geometries

The following scalar functions modify properties of a geometry of type ST_GEOMETRY or one of its subtypes to construct a new geometry:

Table 5. Geospatial scalar functions that construct new geometries from existing geometries
Function Use	Function Name
Create new geometries with different space configurations	ST_BUFFER scalar function ST_DIFFERENCE scalar function ST_INTERSECTION scalar function ST_SYMDIFFERENCE scalar function
Create a new geometry by combining multiple geometries	ST_UNION scalar function

Information about geometries

The following scalar functions return information about geometric properties such as coordinates, measures, and boundaries:

Table 6. Geospatial scalar functions that return information about properties of geometries
Function Use	Function Name
Return information about geometry types	ST_GEOMETRYTYPE scalar function
Return information to indicate whether a geometry is simple	ST_ISSIMPLE scalar function
Return information about geometry dimensions	ST_AREA scalar function
Return information about geometry definitions	ST_NUMPOINTS scalar function
Return information about coordinates and measures	ST_ISVALID scalar function ST_MAXX scalar function ST_MAXY scalar function ST_MINX scalar function ST_MINY scalar function
Return information about spatial reference systems	ST_SRSID scalar function ST_SRSNAME scalar function

Creation of geohashes

The following table functions create geohashes

Table 7. Geospatial table functions that create geohash data
Function Use	Function Name
Create the geohash value for a specific point	ST_GEOHASHVALUE scalar function ST_GEOHASH table function
Create the set of geohash cells that are needed to completely cover a particular geometry	ST_GEOHASHCOVER table function ST_GEOHASHCOVEREXTEND table function
Create the set of geohash cells that are needed to create a boundary box around a particular geometry	ST_FUZZYGEOHASHCOVER table function ST_FUZZYGEOHASHCOVEREXTEND table function