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72f5dcb91f
It’s been superceded by the ‘Local’ library (formerly ‘Electoral wards in the United Kingdom’). The latter is better because: - it’s covers all 4 nations, not just England and Wales - it has electoral wards as well as local authorities which group them, so there’s more flexibility when choosing an area to broadcast to
165 lines
4.8 KiB
Python
Executable File
165 lines
4.8 KiB
Python
Executable File
#!/usr/bin/env python
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from copy import deepcopy
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from pathlib import Path
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import geojson
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import shapely.geometry as sgeom
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from repo import BroadcastAreasRepository
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package_path = Path(__file__).resolve().parent
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def convert_shape_to_feature(shape):
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return {
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"type": "Feature",
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"properties": {},
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"geometry": sgeom.mapping(shape),
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}
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def simplify_polygon(series):
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polygon, *_holes = series # discard holes
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approx_metres_to_degree = 111320
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# initially buffer (extend area past perimeter) by ~25m
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buffer_degrees = 500 / approx_metres_to_degree
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# initially simplify (snap to closest point) by ~25m
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simplify_degrees = 50.0 / approx_metres_to_degree
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starting_polygon = sgeom.LineString(polygon).buffer(buffer_degrees)
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simplified_polygon = None
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num_polys = len(polygon)
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last_num_polys = []
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while True:
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simplified_polygon = starting_polygon.simplify(simplify_degrees)
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simplified_polygon = [[c[0], c[1]] for c in simplified_polygon.exterior.coords]
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num_polys = len(simplified_polygon)
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simplify_degrees *= 2
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if num_polys <= 99 or last_num_polys[-3:] == [num_polys, num_polys, num_polys]:
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break
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last_num_polys.append(num_polys)
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print(".", end="", flush=True) # noqa: T001
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return [simplified_polygon]
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def simplify_geometry(feature):
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if feature["type"] == "Polygon":
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feature["coordinates"] = simplify_polygon(feature["coordinates"])
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return feature
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elif feature["type"] == "MultiPolygon":
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feature["coordinates"] = [
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simplify_polygon(polygon)
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for polygon in feature["coordinates"]
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]
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return feature
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else:
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raise Exception("Unknown type: {}".format(feature["type"]))
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repo = BroadcastAreasRepository()
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repo.delete_db()
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repo.create_tables()
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simple_datasets = [
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("Countries", "ctry19cd", "ctry19nm"),
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]
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for dataset_name, id_field, name_field in simple_datasets:
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filepath = package_path / "{}.geojson".format(dataset_name)
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dataset_id = id_field[:-2]
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dataset_geojson = geojson.loads(filepath.read_text())
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repo.insert_broadcast_area_library(dataset_id, dataset_name, False)
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for feature in dataset_geojson["features"]:
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f_id = dataset_id + "-" + feature["properties"][id_field]
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f_name = feature["properties"][name_field]
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print(f_name) # noqa: T001
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simple_feature = deepcopy(feature)
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simple_feature["geometry"] = simplify_geometry(simple_feature["geometry"])
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repo.insert_broadcast_areas([[
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f_id, f_name,
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dataset_id, None,
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feature, simple_feature,
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]])
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# https://geoportal.statistics.gov.uk/datasets/wards-may-2020-boundaries-uk-bgc
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# Converted to geojson manually from SHP because of GeoJSON download limits
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wards_filepath = package_path / "Electoral Wards May 2020.geojson"
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# http://geoportal.statistics.gov.uk/datasets/ward-to-westminster-parliamentary-constituency-to-local-authority-district-december-2019-lookup-in-the-united-kingdom/data
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las_filepath = package_path / "Electoral Wards and Local Authorities 2020.geojson"
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ward_code_to_la_mapping = {
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f["properties"]["WD19CD"]: f["properties"]["LAD19NM"]
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for f in geojson.loads(las_filepath.read_text())["features"]
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}
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ward_code_to_la_id_mapping = {
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f["properties"]["WD19CD"]: f["properties"]["LAD19CD"]
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for f in geojson.loads(las_filepath.read_text())["features"]
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}
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dataset_name = "Local authorities"
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dataset_id = "wd20-lad20"
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repo.insert_broadcast_area_library(dataset_id, dataset_name, True)
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areas_to_add = []
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for f in geojson.loads(wards_filepath.read_text())["features"]:
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ward_code = f["properties"]["wd20cd"]
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ward_name = f["properties"]["wd20nm"]
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ward_id = "wd20-" + ward_code
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print(ward_name) # noqa: T001
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try:
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la_id = "lad20-" + ward_code_to_la_id_mapping[ward_code]
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la_name = ward_code_to_la_mapping[ward_code]
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sf = deepcopy(f)
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sf["geometry"] = simplify_geometry(sf["geometry"])
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areas_to_add.append([
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ward_id, ward_name,
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dataset_id, la_id,
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f, sf
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])
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except KeyError:
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print("Skipping", ward_code, ward_name) # noqa: T001
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repo.insert_broadcast_areas(areas_to_add)
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areas_to_add = []
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las_filepath = package_path / "Local Authorities May 2020.geojson"
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for feature in geojson.loads(las_filepath.read_text())["features"]:
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la_id = feature["properties"]["lad20cd"]
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group_name = feature["properties"]["lad20nm"]
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print(group_name) # noqa: T001
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group_id = "lad20-" + la_id
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simple_feature = deepcopy(feature)
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simple_feature["geometry"] = simplify_geometry(simple_feature["geometry"])
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areas_to_add.append([
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group_id, group_name,
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dataset_id, None,
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feature, simple_feature
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])
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repo.insert_broadcast_areas(areas_to_add)
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