Contents
How to use PostGIS topologies to clean-up road networks?
This article gives a few basics to get started with using the PostGIS topology extension. We will take avandtage of topologies to clean-up a real topological road network, coming from Toulouse OpenData files. A topology is a general concept, where objects are defined by their relationships instead of their geometries.
Is there a way to enable PostGIS support?
In order to enable PostGIS support you need to be equipped with the following: Move under the topology/ directory and run: No C libs involved so far, so no need to make install. To uninstall/disable just drop the ‘topology’ schema. It contains all the objects installed by the topology.sql script (remember to cascade).
How to use PostGIS topologies in Ubuntu 12.04?
On Ubuntu 12.04, you just have to install PostGIS : The topology extension is installed by default. Just activate it in your database: Load your shapefile (using command-line) like usual : schema=”public.”
Can you store topological elements in PostGIS topology?
Please refer to PostGIS Topology section of manual for details. With topology support enabled you can store topological elements , define TopoGeometry objects as being composed by these elements, convert TopoGeometry objects to simple Geometry objects to use all functions defined on the latter.
How is PostGIS used to clean up junctions?
Create and associate the PostGIS topology: Convert linestrings to vertices and edges within the topology : From now on, we have a topology, whose imperfections were corrected. It smoothly merged all dirty junctions, whose defects were at most 1.0 meter wide. You may enconter insertion problems : the tool fails [1] and aborts the whole transaction.
What does it mean to clean a dataset?
Also known as data cleansing, it entails identifying incorrect, irrelevant, incomplete, and the “dirty” parts of a dataset and then replacing or cleaning the dirty parts of the data. Although sometimes thought of as boring, data cleansing is very valuable in improving the efficiency of the result of data analysis.