PostGISのST_Simplifyを使うとPOLYGONやLINESTRINGの形状を単純化できる。
GeoDjangoからはGEOSGeometryのsimplifyメソッドを使えばよい。
Django1.3で試した。
>>> line_string.simplify? Type: instancemethod Base Class: <type 'instancemethod'> String Form: <bound method LineString.simplify of <LineString object at 0xa4ed5f0>> Namespace: Interactive File: /usr/local/lib/python2.6/dist-packages/Django-1.3-py2.6.egg/django/contrib/gis/geos/geometry.py Definition: line_string.simplify(self, tolerance=0.0, preserve_topology=False) (中略) >>> line_string <LineString object at 0xa4ed5f0> >>> len(line_string) 4367 >>> line_string[:3] [(138.67654300000001, 35.492500999999997, 944.62300000000005), (138.676545, 35.4925, 944.62300000000005), (138.676546, 35.492499000000002, 944.63)] >>> simplified = line_string.simplify(0.001) >>> len(simplified) 90 >>> simplified2 = line_string.simplify(0.001, True) >>> len(simplified2) 2458
