Centerline¶
Summary¶
Centerline (ie. medial axis) of the input polygons based on an auxiliary stream network and, optionally, a DEM to orient the centerline from upstream to downstream.
Tags:vector, polygon, medial axis, disaggregation, model, centerline, valley, line orientation, dem
Usage¶
Compute the medial axis of a polygon. Orient lines from upstream to downstream if provided DEM. Useful for computing centerlines of a valley bottom or any other polygon for which you have a corresponding stream network.
If a stream network is not available for your polygon (ex. historical channel), it is possible to use instead a created LineString which cut the polygon boundaries upstream and downstream. This LineString needs to be an approximation of the medial axis to guide the centerline computation.
Algorithm:
Intersect the input polygon boundaries with the stream network
Keep the most distant resulting points (upstream and downstream points)
Cut the input polygon boundaries with the upstream and downstream points (get two polygon sides)
Compute Voronoi polygons with points on the sides and dissolve it on each side
Cut the Voronoi lines with the input polygon
Remove duplicate lines
Drape lines on DEM
Check/Fix links orientation
The resulting centerline is oriented from upstream to downstream if you provided a DEM.
Parameters¶
| Parameter | Description | Type |
|---|---|---|
Input polygon
POLYGON
|
Polygon to compute the centerline. | Polygon |
Stream network or up/downstream polyline (see doc)
STREAM
|
Stream polyline to compute the upstream and downstream points. ex. french BDCarthage. | LineString |
Disaggregation distance
DISTANCE
|
Distance between points on the input polygon sides to compute the
Voronoi polygons. The smaller the distance, the smoother the result will be.
Default value: 25.0
|
Number |
Input DEM
DEM
(Optional)
|
Digital Elevation Model.
Default value: [3]
|
Raster |
Output Centerline
OUT_CENTERLINE
|
Resulting Centerline. | LineString |