Hi, Tobias, Tobias Nothdurft wrote:
>> Databases provide you with a higher layer of abstraction. With PostGIS, >> you can e. G. load all your linestrings in a table, create an >> geometrical index on it, and then easily and efficiently fetch all >> linestrings in a specific area with a query like: >> >> SELECT * FROM mytable WHERE the_geom && 'BOX(1 2,3 4)'::box2d; > > That sounds nice. > > So I can use a SQL commando like the above instead of using a quadtree? When you use PostGIS, yes. You've got the power and drawbacks of a full relational database. The query above simply fetches all geometries whose bounding box overlaps with the given region. More complex queries and operations are possible. PostGIS includes a GIST-based R-Tree implementation, so you can add a spatial index to your data table which speeds up the query, especially when only a small fraction of the data is actually matching your condition. HTH, Markus -- Markus Schaber | Logical Tracking&Tracing International AG Dipl. Inf. | Software Development GIS Fight against software patents in Europe! www.ffii.org www.nosoftwarepatents.org
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