parenx 0.4.8

GeoJSON network simplification using raster image skeletonization and Voronoi polygons

parex

Simplify (or "pare") a GeoJSON network ("nx") using raster image skeletonization an Voronoi polygons

This uses image skeletonization or Voronoi polygons to simplify network, and output GeoPKG layers corresponding to the input, simplified and primal network. Where a primal network only contains straight line segments

The sample data set is of the Princes Street in Edinburgh, kindly shared by Robin Lovelace

Installation

To install the following will install the project into an activated python virtual environment:

(venv) $ pip install parenx

This places the skeletonization.py and voronoi.py scripts into the executable search path

Examples

A bash helper script run.sh and example data is available under the sitepackage project directory under venv. The exact path varies with module and python version

Skeletonization

The following creates a simplified network by applying skeletonization to a buffered raster array in output.gpkg

(venv) $ ./skeletonize.py data/rnet_princes_street.geojson

Voronoi

The following creates a simplified network by creating set of Voronoi polygons from points on the buffer in output.gpkg

(venv) $ ./voronoi.py data/rnet_princes_street.geojson

Simple operation

The run.sh script sets a python virtual environment and executes the script against a data file in the data directory

$ ./run.sh

The run.sh script optionally takes a filename and file-extension. To simplify a file, say somewhere.geojson and output to GeoPKG files sk-simple.gpkg and vr-simple.gpkg

$ ./run.sh somewhere.geojon simple

Locating the run.sh script

To copy the run.sh script into your local directory the following could help

$ find . -name run.sh -exec cp {} . \;

Notes

Both are the skeletonization and Voronoi approach are generic approaches, with the following known issues:

• This does not maintain a link between attributes and the simplified network
• This does not identify a subset of edges that need simplification
• The lines are a bit wobbly
• It is quite slow