Source code for geometric_features.aggregation.ocean.moc_basins

import shapely.geometry
import shapely.ops
import copy

from geometric_features import FeatureCollection

[docs] def moc(gf): """ Aggregate features defining the ocean basins used in computing the meridional overturning circulation (MOC) Parameters ---------- gf : ``GeometricFeatures`` An object that knows how to download and read geometric features Returns ------- fc : ``FeatureCollection`` The new feature collection """ # Authors # ------- # Xylar Asay-Davis MOCSubBasins = {'Atlantic': ['Atlantic'], 'AtlanticMed': ['Atlantic', 'Mediterranean'], 'IndoPacific': ['Pacific', 'Indian'], 'Pacific': ['Pacific'], 'Indian': ['Indian']} MOCSouthernBoundary = {'Atlantic': '34S', 'AtlanticMed': '34S', 'IndoPacific': '34S', 'Pacific': '6S', 'Indian': '6S'} fc = FeatureCollection() fc.set_group_name(groupName='MOCBasinRegionsGroup') # build MOC basins from regions with the appropriate tags for basinName in MOCSubBasins: tags = ['{}_Basin'.format(basin) for basin in MOCSubBasins[basinName]] fcBasin ='ocean', objectType='region', tags=tags, allTags=False) fcBasin = fcBasin.combine(featureName='{}_MOC'.format(basinName)) maskName = 'MOC mask {}'.format(MOCSouthernBoundary[basinName]) fcMask ='ocean', objectType='region', featureNames=[maskName]) # mask out the region covered by the mask fcBasin = fcBasin.difference(fcMask) # remove various small polygons that are not part of the main MOC # basin shapes. Most are tiny but one below Australia is about 20 # deg^2, so make the threshold 100 deg^2 to be on the safe side. fcBasin = _remove_small_polygons(fcBasin, minArea=100.) # add this basin to the full feature collection fc.merge(fcBasin) return fc
def _remove_small_polygons(fc, minArea): """ A helper function to remove small polygons from a feature collection Parameters ---------- fc : ``FeatureCollection`` The feature collection to remove polygons from minArea : float The minimum area (in square degrees) below which polygons should be removed Returns ------- fcOut : ``FeatureCollection`` The new feature collection with small polygons removed """ # Authors # ------- # Xylar Asay-Davis fcOut = FeatureCollection() removedCount = 0 for feature in fc.features: geom = feature['geometry'] add = False if geom['type'] not in ['Polygon', 'MultiPolygon']: # no area to check, so just add it fcOut.add_feature(copy.deepcopy(feature)) else: featureShape = shapely.geometry.shape(geom) if featureShape.geom_type == 'Polygon': if featureShape.area > minArea: add = True else: removedCount += 1 else: # a MultiPolygon outPolygons = [] for polygon in featureShape.geoms: if polygon.area > minArea: outPolygons.append(polygon) else: removedCount += 1 if len(outPolygons) > 0: outShape = shapely.ops.unary_union(outPolygons) feature['geometry'] = shapely.geometry.mapping(outShape) add = True if add: fcOut.add_feature(copy.deepcopy(feature)) return fcOut