Frequently Asked Questions¶
QH6214 qhull input error: not enough points to construct initial simplex¶
This error occurs when there is an inconsistency in units. For example,
the input data is in EPSG:4326 which uses
degrees, whereas the create_centerline script’s default border
density is in meters.
There are two possible solutions to this problem:
Specify the border density in degrees
$ create_centerlines input.shp output.geojson 0.000012. Transform the input data into a metric system (e.g. EPSG:3857)
The level of detail is too high/The geometry is too complex¶
Adjust the create_centerline’s border density parameter. The script is
ment to serve a wide range of applications, some of which require a
higher level of detail.
Since the Voronoi diagram is used to calculate the centerline’s geometry, that means that depending on the specified border density occasionaly the centerline will have a few branches sticking out. The branches can be removed manually using QGIS.
Number of produced ridges is too small¶
Depending on the polygon’s structure and the border density parameter set by the user, the Voronoi algorithm might not be able to produce enough vertices that lie completely inside the polygon (i.e. do not intersect the polygon’s boundary). In that case, the output centerline can be reduced to a single line or even a single point.
When the centerline consists of less than two lines, the TooFewRidgesError
is raised, the create_centerline script skips the geometry in
question and continues processing the other geometries.
