Geojson and pyproj interop

Sean Gillies

2008-09-18 00:00

I've just finished writing a module that supports projection of objects that provide the geometry part of the Lab's geo interface: proj.py. Maybe you'll find it useful. What it does is take a geojson geometry (or Shapely geometry) and return a new projected geojson geometry object:

>>> from pleiades.openlayers.proj import Transform, PROJ_900913
>>> transform = Transform(PROJ_900913)

>>> # Point, forward
>>> from geojson import Point
>>> point = Point(coordinates=(25.0, 25.0))
>>> fwd = transform(point)
>>> fwd
Point(coordinates=(2782987.269831839, 2875744.6243522423))

>>> # Point, inverse
>>> inv = transform(fwd, inverse=True)
>>> inv
Point(coordinates=(24.999999999999996, 24.999999999999996))

>>> # Line, forward
>>> from geojson import LineString
>>> line = LineString(coordinates=((25.0, 25.0), (30.0, 30.0)))
>>> fwd = transform(line)
>>> fwd
LineString(coordinates=((2782987.269831839, 2875744.6243522423), ...))

>>> # Line, inverse
>>> inv = transform(fwd, inverse=True)
>>> inv
LineString(coordinates=((24.999999999999996, 24.999999999999996), ...))

There's also an object hook if you'd like the transform to yield instances of your own classes.