Python – Merging Multiple Overlapping Lines

Question

I have a shapefile with different line features, some of which overlap. Is there a way to easily merge all overlapping lines into one, new feature using Python?

I've seen some solutions for overlapping polygons, but have had a lot more trouble finding examples using lines.

Answer 1

In Python using the fiona library to read the file and shapely to do the geometry operations it's easy to merge the geometries. For example:

import fiona
import shapely.geometry
import shapely.ops

with fiona.open(path) as src:
    merged_geometries = shapely.ops.linemerge([
        shapely.geometry.shape(feature["geometry"]) for feature in src])

The merged geometry will either be a LineString or a MultiLineString depending on whether a single contiguous line can be formed or not.

You can then write the result back out to a shapefile using fiona (see the docs on writing files), or really do whatever you like with it.

with fiona.open(path) as src:
    crs = src.crs
    driver = src.driver

schema = {
    "geometry": merged_geometries.geom_type,
    "properties": {
        "length": "float"
    }
}

with fiona.open(out_path, "w", driver=driver, crs=crs, schema=schema) as dest:
    dest.write({
        "geometry": shapely.geometry.mapping(merged_geometries),
        "id":"-1",
        "properties": {
            "length": merged_geometries.length
        }
    })