Spatial Database Tips & Tricks Paul Ramsey

It’s not dead, it’s just resting…

Motivation Spatial databases are powerful Godlike, really You do not need “GIS software” Your database is “GIS software” You do not need “spatial middleware” See above

Standard Database Has data types –varchar –integer –real –date

Spatial Database Has spatial data types –point –linestring –polygon –multipoint –multilinestring –multipolygon

Standard Database Has one-dimensional indexes –b-tree –hash

Spatial Database Has spatial indexes –r-tree –quad-tree –grid

Find intersecting shapes…

Start with all boxes,

find intersecting boxes,

then find intersecting shapes.

Standard Database Has functions Work against standard types –lower()‏ –round()‏ –substring()‏ –trim()‏ –dayofweek ()‏

Spatial Database Has spatial functions Work against spatial types –ST_Area(geometry)‏ –ST_Distance(geometry,geometry)‏ –ST_Intersects(geometry,geometry)‏ –ST_DWithin(geometry,geometry,radius)‏ –ST_Union(geometry,geometry)‏

Open Geospatial Consortium (OGC)‏ Simple Features for SQL (SFSQL)‏

Locator Spatial

No buffer operation No union operation No intersection operation No centroid point No area or length calculation L O C A T O R

Linear referencing system (LRS) support Spatial analysis and mining functions and procedures (SDO_SAM package)‏ Geocoding support (SDO_GCDR package)‏ GeoRaster support Topology data model Network data model S P A T I A L

SFSQL compliant New release, not as many features No coordinate reference system transforms Windows only Grid index

SELECT * FROM the_table WHERE the_geom.STIntersects( geometry::STGeomFromText('POINT(0 0)',0)‏ ); SELECT * FROM the_table WHERE ST_Intersects( the_geom, ST_GeomFromText('POINT(0 0)',0)‏ );

PostgreSQL / PostGIS SFSQL compliant Open source (GPL)‏ Proprietary / open source clients “geographic” coordinates require care