crossroads-schematization 0.2.13

Crossroads schematization is a python tool that produces automatic schematization of intersections from OpenStreetMap.

Crossroads schematization

Generate a schematization of an intersection from OpenStreetMap data.

Installation

With pip, use the following command line to install crschem:

• pip install crossroads-schematization

Dependancies:

Crossroads schematization depends on crmodel, that implies the following cascading dependancies:

• crossroadsdescriber
• crossroads-segmentation
• OSMnx
• NetworkX, geopandas

Usage

If you installed crossroads-schematization using pip, a console script is now available using get_crossroad_schematization. This script is also available in the examples folder (PYTHONPATH=$PWD examples/get-crossroad-schematization.py). You will find a complete description of the parameters using --help.

Pipeline

First compute for each branch two long edges S1 and S2 corresponding to the sidewalks:

• for each edge part of a branch, identify the corresponding polyline (continue a couple of 10 meters outside of the crossing)
• fit a long edge E on this polyline, starting from the beginning of the polyline (e.g. 50 meters for example), and with a fixed length in the exterior direction)
• estimate the width of the way (using the number of lanes, the classification of the way)
• reconstruct a linear description of the sidewalk by shifting E
• if the branch is composed of more than one way, identify the two adjacent sidewalks and make them parallel

Each sidewalk is part of two branches (see crossroads-description by Jérémy Kalsron), thus is described by two long edges [Sa_i, Sa_e] and [Sa_i, Sa_e] (e for exterior, i for interior).

• we compute the intersection $m$ between Sa and Sb, and build a new representation with a polyline made of 3 points: Sa_e, m, Sb_e
• If a one of the original segments of the crossing intersects Sa-m-Sb, the sidewalk is described by a polyline made of 4 points: Sa_e, Sa_i, Sb_i, Sb_e

The inner part of the crossroad is computed by assembling all the sidewalks as a closed polyline (assembling each polyline at they extremity). From this region, we can apply a negative buffer to obtain the inner part of the road (with a white space between sidewalks and inner part of the road).

Each traffic island is available as a polygon from crossroads-description. We compute its compactness and size. A description is produced depending on these parameters:

• if the traffic island is large, the rendering is done as if it was bordered by sidewalks
• if the traffic island is small:
  • if the shape is compact, we describe it by a disc
  • if the shape is not compact, we describe it by two half discs connected by lines (a long shape)

Each pedestrian crossing is described by a dedicated pictogram, aligned with the corresponding edge from the initial data