MySQL Meetup

MySQL Spatial ExtensionsAndrew CollinsApril 4th, 2005

Geometry

Curve

LineString

Line LinearRing

Polygon

Surface Geometry-Collection

MultiCurve

Multi-Polygon

Multi-Surface MultiPoint

Multi-LineString

1+

1+

1+

1+

2+

Point

OpenGIS Simple Features Specification for SQLGeometry Class Hierarchy

Non-InstantiableInstantiable

OpenGIS Simple Features Specification for SQLSpatial Data Model

MultiPoint

Geometry-Collection

Multi-LineString

Multi-Polygon

LinearRingPoint LineString

Polygon

SFS Methods : Basic● GeometryType()

– “POINT”, “POLYGON”, “LINEARRING” ...● Envelope()

– Polygon consisting of corner points of bounding box: ((MINX, MINY), (MAXX, MINY), (MAXX, MAXY), (MINX, MAXY), (MINX, MINY))

● AsText()– Returns string representation of the geometry in

Well-Known Text (WKT) format● ... and a few other basic methods

SFS Methods : Spatial Relations● Intersects(anotherGeometry : Geometry)

– Returns true if this Geometry 'spatially intersects' anotherGeometry.

● Touches(anotherGeometry : Geometry)– Returns true if this Geometry 'spatially touches'

anotherGeometry.● Contains(anotherGeometry : Geometry)

– Returns true if this Geometry 'spatially contains' anotherGeometry.

● ... and a few other spatial relational methods:– Equals(...), Disjoint(...), Crosses(...), Within(...),

Overlaps(...), and Relate(...)

SFS Methods : Spatial Analysis● Distance(anotherGeometry : Geometry)

– Return shortest distance between this Geometry and anotherGeometry.

● Union(anotherGeometry : Geometry)– Returns the point set union of this Geometry and

anotherGeometry.● Difference(anotherGeometry : Geometry)

– Returns the point set difference of this Geometry and anotherGeometry.

● ... and a few other spatial relational methods:– SymDifference(anotherGeometry : Geometry),

Buffer(distance : Double), ConvexHull( ), ...

“Not Yet Implemented”● The OpenGIS SFS specification is great, but...

– ... the spatial extensions are only available as of MySQL 4.1.x

– ... and the SFS specification is not fully implemented.

● Many of the spatial relations and analysis methods are “not yet implemented.”– This is understandable given the fact that “robust”

implementations of these methods are not easy to create.

JTS Topology Suite● The JTS Topology Suite

GML : Geography Markup Language

● Another OpenGIS specification used to format Simple Features in XML– XSLT available to translate GML to WKT– ... and MySQL INSERT commands

Links● Open Geospatial Consortium, Inc. (OGC)

http://www.opengeospatial.org/

● OGC: Simple Features - SQL (SFS)http://www.opengeospatial.org/docs/99-049.pdf

● Spatial Extensions in MySQL http://dev.mysql.com/doc/mysql/en/spatial-extensions-in-mysql.html

● Geography Markup Language (GML3.0)http://www.opengeospatial.org/specs/?page=specs

● JTS Topology Suitehttp://www.vividsolutions.com/jts/JTSHome.htm