Coordinate reference systems for Fiona

import logging
import sys

from pyproj import Proj, transform

from fiona import collection

logging.basicConfig(stream=sys.stderr, level=logging.INFO)

with collection("docs/data/test_uk.shp", "r") as input:

    schema = input.schema.copy()

    # This is the input reference system.
    p_in = Proj(input.crs)

    with collection(
            "with-pyproj.shp", "w", "ESRI Shapefile",
            schema=schema,

            # New for 0.6: we can write coordinate reference systems.
            crs={'init': "epsg:27700"}

            ) as output:

        # This is the output reference system.
        p_out = Proj(output.crs)

        for f in input:

            try:
                assert f['geometry']['type'] == "Polygon"

                # Transform the coordinates of every ring.
                new_coords = []
                for ring in f['geometry']['coordinates']:
                    x, y = transform(p_in, p_out, *zip(*ring))
                    new_coords.append(zip(x, y))

                f['geometry']['coordinates'] = new_coords
                output.write(f)

            except Exception, e:
                # Writing untransformable features to a different shapefile
                # is another option.
                logging.exception("Error transforming feature %s:", f['id'])