OSDB2_PostGIS_Presentation.ppt

Building a Spatial Databasein PostgreSQL David Blasby Refractions Researchdblasby@ Introduction PostGIS is a spatial extension for PostgreSQL PostGIS aims to be an “OpenGIS Simple Features for SQL” compliant spatial database I am the principal developer Topics of Discussion Spatial data and spatial databases Adding spatial extensions to PostgreSQL OpenGIS and standards Why PostGIS? There aren’t any good open source spatial databases available commercial ones are very expensive Aren’t any open source spatial functions extremely difficult to properly code building block for any spatial project Enable information to be organized, visualized, and analyzed like never before What is a Spatial Database? Database that: Stores spatial objects Manipulates spatial objects just like other objects in the database What is Spatial data? Data which describes either location or shapee.g.House or Fire Hydrant location Roads, Rivers, Pipelines, Power lines Forests, Parks, Municipalities, Lakes What is Spatial data? In the abstract, reductionist view of the computer, these entities are represented as Points, Lines, and Polygons. Topic Three Land Use Classifications arerepresented as Polygons Topic Three Combination of all the previous data Spatial Relationships Not just interested in location, also interested in “Relationships” between objects that are very hard to model outside the spatial domain. The most common relationships are Proximity : distance Adjacency : “touching” and “connectivity” Containment : inside/overlapping Spatial Relationships Distance between a toxic waste dump and a piece of property you were considering buying. Spatial Relationships Distance to various pubs Spatial Relationships Adjacency: All the lots which share an edge Connectivity: Tributary relationships in river networks Spatial Relationships Containment: Rivers inside watersheds and land (islands) inside lakes Spatial Relationships Stream side logging - adjacency and containment. M