![Common workflow
1. Load/populate table
2. Add geometry column with certain
dimensions and spatial reference
system (SRS/SRID)
3. [Register geometry column in
geometry_columns table]
4. Optimise performance by:
– Creating spatial index
– Clustering data based on spatial index](https://image.slidesharecdn.com/pgintropart1-theoryslides-120220080343-phpapp02/85/Pg-intro-part1-theory_slides-14-320.jpg)
Pg intro part1-theory_slides
- 1. Building Location Aware Apps - Get Started with PostGIS PART I Lasma Sietinsone [email protected]
- 3. Who am I? • Work for EDINA, University of Edinburgh • GIS Technician & Database Engineer • Manage UK data for online maps & services (approaching terabytes of data!) • Provide geo-support for spatially enabled apps
- 4. My Aim? • Stimulate your creative thinking! • Give you an ability to integrate spatial technologies in your own stuff! Space is a natural join between otherwise seemingly unrelated things! • Save you hours/days of faffing around on your own! • Give you a kick for accelerated learning of new technology! Hands-on! I MUST get you rolling independently!
- 5. Who are you? • Who attended prep-workshop? • Experience of audience: – SQL? – RDBMS? – OS? • This demo requires: – SQL – basic knowledge (SELECT, UPDATE, DELETE) – check your cheat-sheet! – RDBMS – none – Windows but Mac OS, Linux will do too
- 6. Contents 1. Pre-workshop (Install and configure PostgreSQL 9.1 with PostGIS 1.5) 2. Some background (~15 mins) 3. Practical (1hr & 15 minutes): • Import some data • Use some PostGIS functions • View data externally • Demo with OpenStreetMap data to perform location based queries 4. Questions and answers (~15 mins)
- 7. What is PostgreSQL? • Proper object-relational database management system • Massive OS project • Super advanced • Fast! • Standard compliant • Well documented • Global user community
- 8. Advantages of a DBMS • Data Independence from application programs • Efficient Data Access • Data Integrity and Security • Centralized Data Administration • Concurrent Access and Crash Recovery • Reduced Application Development Time – common data access functions
- 9. PostGIS what? PostGIS is a spatial extension to the PostgreSQL object-relational database that supports work with geographic data
- 10. PostGIS extension provides • Geometry/geography data types for points, linestrings, polygons, curves, geometry collections, 3D geometries • Use geometry to store object: (A) shape (B) centroid (C) bounding box
- 11. PostGIS extension provides (cont.) • Spatial operators such as contains @, overlaps, intersects &&, same as =, is to the left/right/below/above • Loads of spatial functions
- 12. Spatial functions • Constructors e.g. ST_GeomFromText(), ST_MakePoint(), ST_MakePolygon • Output e.g. ST_AsGML(), ST_AsGeoJSON(), ST_AsBinary() • Accessors: getters and setters e.g. ST_Transform(), ST_GeometryType(), ST_IsValid(), ST_NPoints(), ST_SetDRID() • Measurement e.g. ST_Distance_Sphere(), ST_Length_2D(), ST_Perimeter(), ST_Azimuth()
- 13. Spatial functions (continued) • Decomposition e.g. ST_Centroid(), ST_Box2D(), ST_Boundary(), ST_GeometryN(), ST_DumpRings() • Composition e.g. ST_MakePoint(), ST_MakePolygon(), ST_BuildArea(), ST_Polygonize() • Simplification e.g. ST_Simplify(), ST_SimplifyPreserveTopology(), ST_SnapToGrid()
- 14. Common workflow 1. Load/populate table 2. Add geometry column with certain dimensions and spatial reference system (SRS/SRID) 3. [Register geometry column in geometry_columns table] 4. Optimise performance by: – Creating spatial index – Clustering data based on spatial index
- 15. Common workflow (continued) 5. View/Edit/Query data with: – desktop GIS, e.g. QGIS, OpenJUMP, GRASS etc. – Web map servers, e.g. GeoServer, MapServer, Deegree etc. – Custom applications communicating via database connectors such as JDBC
- 16. Use online references PostgreSQL docs ***** http://www.postgresql.org/docs/9.0/interacti ve/index.html PostGIS docs ***** http://www.postgis.org/docs/