def kml_chunk(self, n, s, e, w):
"""
Get the kml of a lat/lon bounded part of the study region,
with geometry simplified in proportion to the visible % of the region
"""
bounds = Polygon(LinearRing([Point(w, n), Point(e, n), Point(e, s), Point(w, s), Point(w, n)]))
bounds.set_srid(4326)
center_lat = bounds.centroid.y # in 4326 because it is used only for setting up the subregion calls
center_lon = bounds.centroid.x # in 4326 because it is used only for setting up the subregion calls
bounds.transform(settings.GEOMETRY_DB_SRID)
# all longitudinal width calcs should be done in GEOMETRY_DB_SRID - 4326 can fail across the date line
zoom_width = (Point(bounds.extent[0], bounds.centroid.y)).distance(Point(bounds.extent[2], bounds.centroid.y))
full_shape_width = (Point(self.geometry.extent[0], self.geometry.centroid.y)).distance(Point(self.geometry.extent[2], self.geometry.centroid.y))
# The following simplify values can be tuned to your preference
# minimum geometry simplify value (highest detail) = 50 (arbitrary, based on observation)
# maximum geometry simplify value = 200 (arbitrary, based on observation)
# value set by pecentage of study region width requested in this chunk
min_simplify_val = 50.0
max_simplify_val = 200.0
simplify_factor = max(min_simplify_val, min(max_simplify_val, max_simplify_val * zoom_width / full_shape_width))
transform_geom = self.geometry.simplify(simplify_factor, preserve_topology=True)
transform_geom = transform_geom.intersection(bounds)
transform_geom.transform(4326)
# Debugging info
#print zoom_width
#print full_shape_width
#print simplify_factor
#print transform_geom.num_coords
# End debugging info
# only add sub-regions if this is not our highest detail level
bLastLodLevel = simplify_factor < max_simplify_val # change this last value to build varying levels of LOD
max_lod_pixels = 500
min_lod_pixels = 250
# make sure the most detailed lod stays active no matter how close user zooms
if bLastLodLevel:
max_lod_pixels = -1
retval = '<Region><LatLonAltBox><north>%f</north><south>%f</south><east>%f</east><west>%f</west></LatLonAltBox><Lod><minLodPixels>%f</minLodPixels><maxLodPixels>%f</maxLodPixels><minFadeExtent>0</minFadeExtent><maxFadeExtent>0</maxFadeExtent></Lod></Region>' % (n, s, e, w, min_lod_pixels, max_lod_pixels) + '<Placemark> <name>Study Region Boundaries</name><Style> <LineStyle> <color>ff00ffff</color> <width>2</width> </LineStyle> <PolyStyle> <color>8000ffff</color> </PolyStyle></Style>%s</Placemark>' % (transform_geom.kml,)
# conditionally add sub-regions
if not bLastLodLevel:
subregions = '<Folder><name>Study Region LODs</name>' + '<Folder><name>SE</name>' + self.kml_chunk(center_lat, s, e, center_lon) + '</Folder>'
subregions = subregions + '<Folder><name>NE</name>' + self.kml_chunk(n, center_lat, e, center_lon) + '</Folder>'
subregions = subregions + '<Folder><name>SW</name>' + self.kml_chunk(center_lat, s, center_lon, w) + '</Folder>'
subregions = subregions + '<Folder><name>NW</name>' + self.kml_chunk(n, center_lat, center_lon, w) + '</Folder>'
retval = retval + subregions + '</Folder>'
return retval
def build_box(self):
"""
top_left = (west, north)
top_right = (east, north)
bottom_right = (east, south)
bottom_left = (west, south)
"""
try:
box = Polygon(
LinearRing(
[
Point(float(self.west), float(self.north)),
Point(float(self.east), float(self.north)),
Point(float(self.east), float(self.south)),
Point(float(self.west), float(self.south)),
Point(float(self.west), float(self.north)),
]
)
)
box.set_srid(settings.GEOMETRY_CLIENT_SRID)
return box
except Exception, e:
raise self.InternalException(
"Exception raised in ClipToGraticuleManipulator while initializing graticule geometry: " + e.message
)
def build_box(self):
'''
top_left = (west, north)
top_right = (east, north)
bottom_right = (east, south)
bottom_left = (west, south)
'''
try:
box = Polygon( LinearRing([ Point( float(self.west), float(self.north) ), Point( float(self.east), float(self.north) ), Point( float(self.east), float(self.south) ), Point( float(self.west), float(self.south) ), Point( float(self.west), float(self.north))]))
box.set_srid(settings.GEOMETRY_CLIENT_SRID)
return box
except Exception, e:
raise self.InternalException("Exception raised in ClipToGraticuleManipulator while initializing graticule geometry: " + e.message)
def kml_chunk(self, n, s, e, w):
"""
Get the kml of a lat/lon bounded part of the study region,
with geometry simplified in proportion to the visible % of the region
"""
bounds = Polygon(
LinearRing([
Point(w, n),
Point(e, n),
Point(e, s),
Point(w, s),
Point(w, n)
]))
bounds.set_srid(4326)
center_lat = bounds.centroid.y # in 4326 because it is used only for setting up the subregion calls
center_lon = bounds.centroid.x # in 4326 because it is used only for setting up the subregion calls
bounds.transform(settings.GEOMETRY_DB_SRID)
# all longitudinal width calcs should be done in GEOMETRY_DB_SRID - 4326 can fail across the date line
zoom_width = (Point(bounds.extent[0], bounds.centroid.y)).distance(
Point(bounds.extent[2], bounds.centroid.y))
full_shape_width = (Point(self.geometry.extent[0],
self.geometry.centroid.y)).distance(
Point(self.geometry.extent[2],
self.geometry.centroid.y))
# The following simplify values can be tuned to your preference
# minimum geometry simplify value (highest detail) = 50 (arbitrary, based on observation)
# maximum geometry simplify value = 200 (arbitrary, based on observation)
# value set by pecentage of study region width requested in this chunk
min_simplify_val = 50.0
max_simplify_val = 200.0
simplify_factor = max(
min_simplify_val,
min(max_simplify_val,
max_simplify_val * zoom_width / full_shape_width))
transform_geom = self.geometry.simplify(simplify_factor,
preserve_topology=True)
transform_geom = transform_geom.intersection(bounds)
transform_geom.transform(4326)
# Debugging info
#print zoom_width
#print full_shape_width
#print simplify_factor
#print transform_geom.num_coords
# End debugging info
# only add sub-regions if this is not our highest detail level
bLastLodLevel = simplify_factor < max_simplify_val # change this last value to build varying levels of LOD
max_lod_pixels = 500
min_lod_pixels = 250
# make sure the most detailed lod stays active no matter how close user zooms
if bLastLodLevel:
max_lod_pixels = -1
retval = '<Region><LatLonAltBox><north>%f</north><south>%f</south><east>%f</east><west>%f</west></LatLonAltBox><Lod><minLodPixels>%f</minLodPixels><maxLodPixels>%f</maxLodPixels><minFadeExtent>0</minFadeExtent><maxFadeExtent>0</maxFadeExtent></Lod></Region>' % (
n, s, e, w, min_lod_pixels, max_lod_pixels
) + '<Placemark> <name>Study Region Boundaries</name><Style> <LineStyle> <color>ff00ffff</color> <width>2</width> </LineStyle> <PolyStyle> <color>8000ffff</color> </PolyStyle></Style>%s</Placemark>' % (
transform_geom.kml, )
# conditionally add sub-regions
if not bLastLodLevel:
subregions = '<Folder><name>Study Region LODs</name>' + '<Folder><name>SE</name>' + self.kml_chunk(
center_lat, s, e, center_lon) + '</Folder>'
subregions = subregions + '<Folder><name>NE</name>' + self.kml_chunk(
n, center_lat, e, center_lon) + '</Folder>'
subregions = subregions + '<Folder><name>SW</name>' + self.kml_chunk(
center_lat, s, center_lon, w) + '</Folder>'
subregions = subregions + '<Folder><name>NW</name>' + self.kml_chunk(
n, center_lat, center_lon, w) + '</Folder>'
retval = retval + subregions + '</Folder>'
return retval
