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broadcast-areas: buffer areas by a larger degree

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Signed-off-by: Toby Lorne <toby.lornewelch-richards@digital.cabinet-office.gov.uk>
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Toby Lorne
2020-08-05 12:31:03 +01:00
parent 1301ae4bba
commit dde285ef03
1 changed files with 6 additions and 5 deletions
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11
notifications_utils/broadcast_areas/create-broadcast-areas-db.py
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@@ -25,14 +25,14 @@ def simplify_polygon(series):
approx_metres_to_degree = 111320 approx_metres_to_degree = 111320
# initially buffer (extend area past perimeter) by ~25m # initially buffer (extend area past perimeter) by ~25m
buffer_degrees = 25.0 / approx_metres_to_degree buffer_degrees = 500 / approx_metres_to_degree
# initially simplify (snap to closest point) by ~25m # initially simplify (snap to closest point) by ~25m
simplify_degrees = 25.0 / approx_metres_to_degree simplify_degrees = 50.0 / approx_metres_to_degree
starting_polygon = sgeom.LineString(polygon).buffer(buffer_degrees) starting_polygon = sgeom.LineString(polygon).buffer(buffer_degrees)
simplified_polygon = None simplified_polygon = None
num_polys = len(polygon) num_polys = len(polygon)
last_num_polys = None last_num_polys = []
while True: while True:
simplified_polygon = starting_polygon.simplify(simplify_degrees) simplified_polygon = starting_polygon.simplify(simplify_degrees)
simplified_polygon = [[c[0], c[1]] for c in simplified_polygon.exterior.coords] simplified_polygon = [[c[0], c[1]] for c in simplified_polygon.exterior.coords]
@@ -40,12 +40,13 @@ def simplify_polygon(series):
num_polys = len(simplified_polygon) num_polys = len(simplified_polygon)
simplify_degrees *= 2 simplify_degrees *= 2
if num_polys <= 99 or last_num_polys == num_polys: if num_polys <= 99 or last_num_polys[-3:] == [num_polys, num_polys, num_polys]:
break break
last_num_polys = num_polys last_num_polys.append(num_polys)
print(".", end="", flush=True) # noqa: T001 print(".", end="", flush=True) # noqa: T001
return [simplified_polygon] return [simplified_polygon]