implement LatLngRect.area()

sidewalklabs · May 25, 2016 · 8f53f57 · 8f53f57
1 parent c56e7f1
commit 8f53f57
Show file tree

Hide file tree

Showing 2 changed files with 16 additions and 0 deletions.
diff --git a/s2sphere/sphere.py b/s2sphere/sphere.py
@@ -617,6 +617,16 @@ def get_vertex(self, k):
         return LatLng.from_radians(self.lat().bound(k >> 1),
                                    self.lng().bound((k >> 1) ^ (k & 1)))
 
+    def area(self):
+        """Area in steradians."""
+        if self.is_empty():
+            return 0.0
+
+        return self.lng().get_length() * math.fabs(
+            math.sin(self.lat_hi().radians) -
+            math.sin(self.lat_lo().radians)
+        )
+
     def is_empty(self):
         return self.lat().is_empty()
 

diff --git a/tests/sphere_test.py b/tests/sphere_test.py
@@ -1607,6 +1607,12 @@ def testGetVertex(self):
                                         r.get_vertex((k + 1) & 3).to_point())
                 )
 
+    def testArea(self):
+        self.assertEqual(s2sphere.LatLngRect.empty().area(), 0.0)
+        self.assertEqual(s2sphere.LatLngRect.full().area(), 4 * math.pi)
+        self.assertEqual(self.rect_from_degrees(0, 0, 90, 90).area(),
+                         math.pi / 2)
+
     def testContains(self):
         eq_m180 = LatLng.from_radians(0, -math.pi)
         north_pole = LatLng.from_radians(math.pi / 2.0, 0)