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#!/usr/bin/env python
import math
from django.db import models
from django.conf import settings
from opencontext_py.libs.general import LastUpdatedOrderedDict
from opencontext_py.apps.ocitems.manifest.models import Manifest
from opencontext_py.apps.ocitems.geospace.models import Geospace
class ValidateGeoJson():
"""
Code to validate GeoJSON and make it conform to the "right hand rule"
This code was inspired and adapted from the MapBox created
geojson-rewind repo here:
https://github.com/mapbox/geojson-rewind
The test_good and test_bad coordinate lists
are provided for testing.
"""
WGS84_RADIUS = 6378137
WGS84_FLATTENING = 1/298.257223563
WGS84_POLAR_RADIUS = 6356752.3142
def __init__(self):
# testing good, valid coordinates
self.test_good = [
[
[
78.09974670410156,
9.549969014000085
],
[
78.10009002685545,
9.549969014000085
],
[
78.10009002685545,
9.55030757857335
],
[
78.09974670410156,
9.55030757857335
],
[
78.09974670410156,
9.549969014000085
]
]
]
# testing bad coordinates listed in the wrong direction
self.test_bad = [
[
[
31.13746345405887,
29.975203341460883
],
[
31.1374668398092,
29.9751112230538
],
[
31.137198093520578,
29.975172011251605
],
[
31.137196168430933,
29.975292096585992
],
[
31.13730958971869,
29.975293360313724
],
[
31.137304125266812,
29.975283862123206
],
[
31.137301269522542,
29.975270727601224
],
[
31.137302412179583,
29.97525816424525
],
[
31.13730812276983,
29.97524445855201
],
[
31.137319543950362,
29.97522961052095
],
[
31.137334962633908,
29.975218188717694
],
[
31.1373480978,
29.97520848041729
],
[
31.13736751398653,
29.975203341460883
],
[
31.137376911262734,
29.975204253462266
],
[
31.13739773151606,
29.975201042003434
],
[
31.137420834388546,
29.975200053742565
],
[
31.137438232060635,
29.975200794549117
],
[
31.13745506020086,
29.975203018525235
],
[
31.13746345405887,
29.975203341460883
]
]
]
def fix_geometry_rings_dir(self, geometry_type, coordinates):
""" fixes the directions of rings of coordinates for
a MultiPolygon or Polygon geometry
"""
if geometry_type == 'MultiPolygon':
# a MultiPoylgon will be a list of Polygons
fixed_coords = []
for poly_coordinates in coordinates:
fixed_poly_coords = self.fix_poly_rings_dir(poly_coordinates)
fixed_coords.append(fixed_poly_coords)
elif geometry_type == 'Polygon':
# is a simple polygon
fixed_coords = self.fix_poly_rings_dir(coordinates)
else:
# don't mess with coordinates we don't understand
fixed_coords = coordinates
return fixed_coords
def validate_all_geometry_coordinates(self, geometry_type, coordinates):
""" Validates the directions of rings of coordinates for
a MultiPolygon or Polygon geometry
Returns True if all rings are valid, False if 1 or more rings
are not valid (in terms of direction)
"""
valid = True
if geometry_type == 'MultiPolygon':
# a MultiPoylgon will be a list of Polygons
for poly_coordinates in coordinates:
rings_ok = self.validate_poly_rings_dir(poly_coordinates)
for ring_ok in rings_ok:
if ring_ok is False:
valid = False
elif geometry_type == 'Polygon':
# is a simple polygon
rings_ok = self.validate_poly_rings_dir(coordinates)
for ring_ok in rings_ok:
if ring_ok is False:
valid = False
else:
# don't mess with coordinates we don't understand
valid = None
return valid
def fix_poly_rings_dir(self, coordinates):
""" makes new coordinates with valid directions
for a polygon geometry
"""
fixed_coords = []
rings_ok = self.validate_poly_rings_dir(coordinates)
len_coords = len(coordinates)
for i in range(0, len_coords):
if rings_ok[i]:
# this ring is valid, so add as is
fixed_coords.append(coordinates[i])
else:
# this ring is not valid, so reverse it
rev_ring = coordinates[i][::-1]
fixed_coords.append(rev_ring)
return fixed_coords
def validate_poly_rings_dir(self, coordinates):
"""
Makes a list of True or False (Valid / Invalid) values
for rings of coordinates in a polygon geometry
(1) The exterior ring should be counterclockwise. This
means ring_area calculatations are NEGATIVE
(2) Interior rings should be clockwise. This means
ring_area calculations should be POSITIVE
See more at: https://stackoverflow.com/questions/1165647/how-to-determine-if-a-list-of-polygon-points-are-in-clockwise-order/1165943#1165943
"""
rings_ok = []
len_coords = len(coordinates)
if len_coords > 0:
for i in range(0, len_coords):
area = self.ring_area(coordinates[i])
if i == 0:
if area < 0:
# exterior ring area less than 0, so VALID
rings_ok.append(True)
else:
# not a valid exterior ring
rings_ok.append(False)
else:
if area < 0:
# negative interiror ring area, so not valid
rings_ok.append(False)
else:
# positive interior ring area, so valid
rings_ok.append(True)
return rings_ok
def polygon_area(self, coordinates):
""" calculates the area of a polygon,
works by subtracting the area of interior
'donut hole' rings
"""
area = 0
len_coords = len(coordinates)
if len_coords > 0:
area += abs(self.ring_area(coordinates[0]))
for i in range(1, len_coords):
# now subtract the area defined by interior rings
area -= abs(self.ring_area(coordinates[i]))
return area
def ring_area(self, coordinates):
""" calculates the area of a ring of coordinates """
area = 0
len_coords = len(coordinates)
if len_coords > 2:
for i in range(0, (len_coords - 1)):
p_a = coordinates[i]
p_b = coordinates[(i + 1)]
area += self.rad(p_b[0] - p_a[0]) \
* (2 + math.sin(self.rad(p_a[1])) \
+ math.sin(self.rad(p_b[1])))
area = area * self.WGS84_RADIUS * self.WGS84_RADIUS / 2
return area
def rad(self, val):
output = val * (math.pi / 180)
return output
"""
# testing
#
from opencontext_py.libs.validategeojson import ValidateGeoJson
v_geojson = ValidateGeoJson()
bad = v_geojson.validate_poly_rings_dir(v_geojson.test_bad)
good = v_geojson.validate_poly_rings_dir(v_geojson.test_good)
fix_bad_coords = v_geojson.fix_poly_rings_dir(v_geojson.test_bad)
fix_bad = v_geojson.validate_poly_rings_dir(fix_bad_coords)
"""