geojson-rewind 1.0.0

A Python library for enforcing polygon ring winding order in GeoJSON

geojson-rewind

A Python library for enforcing polygon ring winding order in GeoJSON

The GeoJSON spec mandates the right hand rule:

A linear ring MUST follow the right-hand rule with respect to the area it bounds, i.e., exterior rings are counterclockwise, and holes are clockwise.

This helps you generate compliant Polygon and MultiPolygon geometries.

Installation

pip install geojson-rewind

Usage

As a Library

Enforce RFC 7946 ring winding order (input/output is a GeoJSON string):

>>> from geojson_rewind import rewind

>>> input = """{
...      "geometry": {   "coordinates": [   [   [100, 0],
...                                             [100, 1],
...                                             [101, 1],
...                                             [101, 0],
...                                             [100, 0]]],
...                      "type": "Polygon"},
...      "properties": {"foo": "bar"},
...      "type": "Feature"}"""

>>> output = rewind(input)

>>> output
'{"geometry": {"coordinates": [[[100, 0], [101, 0], [101, 1], [100, 1], [100, 0]]], "type": "Polygon"}, "properties": {"foo": "bar"}, "type": "Feature"}'

>>> type(output)
<class 'str'>

Enforce RFC 7946 ring winding order (input/output is a python dict):

>>> from geojson_rewind import rewind

>>> input = {
...     'geometry': {   'coordinates': [   [   [100, 0],
...                                            [100, 1],
...                                            [101, 1],
...                                            [101, 0],
...                                            [100, 0]]],
...                     'type': 'Polygon'},
...     'properties': {'foo': 'bar'},
...     'type': 'Feature'}

>>> output = rewind(input)

>>> output
{'geometry': {'coordinates': [[[100, 0], [101, 0], [101, 1], [100, 1], [100, 0]]], 'type': 'Polygon'}, 'properties': {'foo': 'bar'}, 'type': 'Feature'}

>>> type(output)
<class 'dict'>

On the Console

# Enforce ring winding order on a GeoJSON file
$ rewind in.geojson > out.geojson

# fetch GeoJSON from the web and enforce ring winding order
$ curl "https://myserver.com/in.geojson" | rewind

Acknowledgements

geojson-rewind is a python port of Mapbox's javascript geojson-rewind package. Credit to Tom MacWright and contributors.