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notifications-api/app/broadcast_message/translators.py
Chris Hill-Scott c0742fe83d Pass polygons through if they’re small already
If a polygon is smaller than the largest polygon in our dataset of
simplified polygons then we’re only throwing away useful detail by
simplifying it.

We should still simplify larger polygons as a fallback, to avoid sending
anything to the CBC that we’re not sure it will like.

The thresholds here are low: we can raise them as we test and experiment
more.

Here’s some data about the Flood Warning Service polygons

Percentile | 80% | 90%   | 95%    | 98%     | 99%     | 99.9%
-----------|-----|-------|--------|---------|---------|---------
Point count| 226 | 401.9 | 640.45 | 1015.38 | 1389.07 | 3008.609

Percentile    | 80% | 90%   | 95%    | 98%     | 99%     | 99.9%
--------------|-----|-------|--------|---------|---------|---------
Polygon count |2----|3------|5-------|8--------|10-------|40.469
2021-11-18 15:48:45 +00:00

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from bs4 import BeautifulSoup
def cap_xml_to_dict(cap_xml):
# This function assumes that its being passed valid CAP XML
cap = BeautifulSoup(cap_xml, "xml")
return {
"msgType": cap.alert.msgType.text,
"reference": cap.alert.identifier.text,
"cap_event": cap.alert.info.event.text,
"category": cap.alert.info.category.text,
"expires": cap.alert.info.expires.text,
"content": cap.alert.info.description.text,
"areas": [
{
"name": area.areaDesc.text,
"polygons": [
cap_xml_polygon_to_list(polygon.text)
for polygon in area.find_all('polygon')
]
}
for area in cap.alert.info.find_all('area')
]
}
def cap_xml_polygon_to_list(polygon_string):
return [
[
float(coordinate) for coordinate in pair.split(',')
]
for pair in polygon_string.strip().split(' ')
]