80 lines
2.1 KiB
Python
Executable file
80 lines
2.1 KiB
Python
Executable file
#!/bin/python3
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import argparse
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import osmapi
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import shapely
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import pickle
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def chunks(lst, n):
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"""Yield successive n-sized chunks from lst.
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https://stackoverflow.com/a/312464
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CC BY-SA 4.0
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"""
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for i in range(0, len(lst), n):
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yield lst[i:i + n]
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def get_shell_ids(osm_api, ways):
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"""
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Get a list of OSM node IDs
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that forms the shell of the area's polygon.
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"""
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shell_ids = list()
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for way in ways:
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way = osm_api.WayGet(way['ref'])
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node_ids = way['nd']
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if not shell_ids:
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shell_ids.append(node_ids[0])
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for node_id in node_ids[1:]:
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shell_ids.append(node_id)
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return shell_ids
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def get_node_data(osm_api, shell_ids):
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"""Get the data of OSM nodes as a dict of (id -> data)."""
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node_data = dict()
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for chunk in chunks(shell_ids, 100):
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node_data |= osm_api.NodesGet(chunk)
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return node_data
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def get_shell(shell_ids, node_data):
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"""Get the shell of the area's polygon as a list of (lat, lon) tuples."""
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shell = list()
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for shell_id in shell_ids:
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node = node_data[shell_id]
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shell.append((node['lat'], node['lon']))
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return shell
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def main(args):
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osm_api = osmapi.OsmApi()
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rel = osm_api.RelationGet(args.osm_relation_id)
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# Filter out city centre etc.
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ways = filter(lambda x: x['type'] == 'way', rel['member'])
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shell_ids = get_shell_ids(osm_api, ways)
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node_data = get_node_data(osm_api, shell_ids)
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shell = get_shell(shell_ids, node_data)
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polygon = shapely.Polygon(shell)
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with open(args.output_file, 'wb') as f:
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pickle.dump(polygon, f)
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if __name__ == '__main__':
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parser = argparse.ArgumentParser(description="""
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Creates a polygon from an OpenStreetMap relation and saves this
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to a file as a Python pickle.
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""")
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parser.add_argument("osm-relation-id",
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help="OpenStreetMap relation ID", type=int)
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parser.add_argument(
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"-v", "--output-file", help="Output file for the resulting polygon",
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default="polygon.pickle")
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args = parser.parse_args()
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main(args)
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