def lookup_point(request):
"""Find nearby polygons with a point and search radius.
Three lookup methods are supported:
sphericalmercator: radius (in km) is applied to search buffer in
900913 (aka Google Spherical Mercator) projection. This method
is appropriate when used in conjuction with web maps.
greatcircle: uses PostGIS ST_DWithin spatial query on a geography
column, using great circle distances.
point: simple test if point is inside polygons (e.g., radius=0)
These methods assume the geometries are in a Geography column. Edge
cases across the dateline are handled correctly.
Different methods are needed if a regular Geometry column is used
in order to handle cases across the dateline."""
mpa_list = ()
default_method = 'webmercator'
try:
lon = float(request.GET['lon'])
lat = float(request.GET['lat'])
try:
radius = float(request.GET['radius'])
except:
radius = 225.0 # km
try:
method = request.GET['method'] or default_method # set default if empty string passed
except (KeyError):
method = default_method
if method not in ('point', 'greatcircle', 'webmercator', 'webmercator_buffer', 'webmercator_box', 'webmercator_simple'):
raise LookupMethodError('Unknown or malformed lookup method passed in GET query string.')
if (radius == 0):
method = 'point'
except:
# Bad input, return empty list
return render(request, 'wdpa/mpalookup.json', {
'mpa_list': mpa_list,
}, content_type='application/json; charset=utf-8')
else:
# We need to normalize the longitude into the range -180 to 180 so we don't
# make the cast to PostGIS Geography type complain
point = geos.Point(normalize_lon(lon), lat, srid=gdal.SpatialReference('WGS84').srid) # srid=4326 , WGS84 geographic
if (method == 'webmercator'):
if (normalize_lon(lon) < 0):
lon360 = normalize_lon(lon) + 360
else:
lon360 = normalize_lon(lon) - 360
point360 = geos.Point(lon360, lat, srid=gdal.SpatialReference('WGS84').srid)
point.transform(900913) # Google Spherical Mercator srid
point360.transform(900913)
#mpa_list = WdpaPolygon.objects.filter(geom_smerc__dwithin=(point, Distance(km=radius))).defer(*WdpaPolygon.get_geom_fields())
mpa_list = WdpaPolygon.objects.filter(Q(geom_smerc__dwithin=(point, Distance(km=radius))) | Q(geom_smerc__dwithin=(point360, Distance(km=radius)))).defer(*WdpaPolygon.get_geom_fields())
search = point
elif (method == 'webmercator_buffer'):
point.transform(900913) # Google Spherical Mercator srid
searchbuffer = point.buffer(radius * 1000) # convert km to m, create buffer
mpa_list = WdpaPolygon.objects.filter(geog__intersects=searchbuffer).defer(*WdpaPolygon.get_geom_fields())
search = searchbuffer
elif (method == 'webmercator_box'):
point.transform(900913) # Google Spherical Mercator srid
searchbuffer = point.buffer(radius * 1000)
mpa_list = WdpaPolygon.objects.filter(geog__intersects=searchbuffer.envelope).defer(*WdpaPolygon.get_geom_fields()) # use simple bounding box instead
search = searchbuffer.envelope
elif (method == 'webmercator_simple'):
point.transform(900913) # Google Spherical Mercator srid
searchbuffer = point.buffer(radius * 1000, quadsegs=2) # simple buffer with 2 segs per quarter circle
mpa_list = WdpaPolygon.objects.filter(geog__intersects=searchbuffer).defer(*WdpaPolygon.get_geom_fields())
search = searchbuffer
elif (method == 'greatcircle'):
mpa_list = WdpaPolygon.objects.filter(geog__dwithin=(point, Distance(km=radius))).defer(*WdpaPolygon.get_geom_fields())
search = point
elif (method == 'point'):
mpa_list = WdpaPolygon.objects.filter(geog__intersects=point).defer(*WdpaPolygon.get_geom_fields())
search = point
candidate_radius = radius * 2.2 # We're using big icons on a point, this let's us catch it better
mpa_candidate_list = MpaCandidate.objects.filter(geog__dwithin=(point, Distance(km=candidate_radius))).defer(*MpaCandidate.get_geom_fields())
search.transform(4326)
return render(request, 'wdpa/mpalookup.json', {
'search': search.coords,
'mpa_list': mpa_list,
'mpa_candidate_list': mpa_candidate_list,
}, content_type='application/json; charset=utf-8')
