README.md

This repository houses definitions of geometric features. These features can include regions, transects, and points, described in geojson format. For example, here are some regions for Antarctica.

Documentation

http://mpas-dev.github.io/geometric_features/main/

Contributors

Data for regions has been derived from sources listed in the contributors file as specified via the author field in each geojson file.

Quick Start

The python geometric_features package can be used to help maintain and use this repository. Several example scripts that make use of the package can be found in the examples directory. Each of the classes and functions that make up the package have extensive documentation. More user-level documentation will be added shortly.

To use geometric features, you can install it in a conda environment:

conda create -n geometric_features -c conda-forge python=3.13 geometric_features
conda activate geometric_features

To develop geometric_features (e.g. to add new features), create and activate an environment with all of the required dependencies:

conda create -y -n mpas_dev --file dev-spec.txt
conda activate mpas_dev
python -m pip install --no-deps --no-build-isolation -e .

A typical workflow will look like:

• Create a GeometricFeatures object and point it to a location where you have stored (or would like to store) geometry data.
  • gf = GeometricFeatures(localCache='./geometric_data')
• Read in one or more FeatureCollections from the geojson files in the geometric_data directory.
  • fcArctic = gf.read('ocean', 'region', featureNames=['Arctic Ocean'])
  • fcAtlantic = gf.read('ocean', 'region', tags=['Atlantic_Basin'])
• Edit features:
  • Merge, combine, tag, mask out or simplify the features, see below.
  • Use the shapely package to edit the geometry in more sophisticated ways
• Visualize features:
  • fc.plot(projection='cyl')
• Split feature collection back into individual features for inclusion in the repo:
  • gf.split(fc)

Available functionality includes:

• fc.merge(other) - Merge two feature collection together.
• fc.combine() - Combine features into a single feature.
• fc.difference() - Mask features using shapes in a second feature file.
• fc.fix_antimeridian() - Split a feature at the antimeridian (+/- 180 longitude). The resulting feature has all points between -180 and 180 lon.
• fc.set_group_name() - Set the "groupName" property of the FeatureCollection
• fc.tag() - Add one or more tags to the "tag" property of each feature in a collection. This can be useful for reading back a collection of features with that tag.

IMPORTANT: Always use the gf.split(fc) script when placing features into the geometric_data directory. This will help everyone maintain the repository, and allow tools to parse them cleanly.

Many of this functionality can also be accessed with a command-line interface:

merge_features
combine_features
difference_features
set_group_name
split_features
simplify_features
tag_features
plot_features

Use the -h flag to find out more.

An example workflow to read in, plot and write out a set of features is

#!/usr/bin/env python

from geometric_features import GeometricFeatures
import matplotlib.pyplot as plt

# create a GeometricFeatures object that points to a local cache of geometric
# data and knows which branch of geometric_feature to use to download
# missing data
gf = GeometricFeatures(cacheLocation='./geometric_data')

# read in a FeatureCollection containing all ocean regions in the Atlantic
# basin
fcAtlantic = gf.read(componentName='ocean', objectType='region',
                     tags=['Atlantic_Basin'])

fcAtlantic.plot('cyl')
plt.title('Atlantic merged')

# combine them all into a single feature
fcAtlantic = fcAtlantic.combine(featureName='Atlantic_Basin')
fcAtlantic.plot('cyl')
plt.title('Atlantic combined')

# make another feature containing the regions in Filchner-Ronne Ice Shelf
fcFilchnerRonne = gf.read(componentName='iceshelves', objectType='region',
                          featureNames=['Filchner_1', 'Filchner_2',
                                        'Filchner_3', 'Ronne_1', 'Ronne_2'])
fcFilchnerRonne.plot('southpole')
plt.title('Filchner-Ronne')


# make one more collection of all the IMBIE basins in West Antarctica
fcWestAntarctica = gf.read(componentName='landice', objectType='region',
                           tags=['WestAntarcticaIMBIE'])

fcWestAntarctica.plot('southpole')
plt.title('West Antarctica')

fcWestAntarctica.to_geojson('west_antarctica.geojson')
plt.show()