[GIS] Python Library for converting GeoJSON Multi-polygon to polygon

geojsongeometry-conversionpolygonpython

I would like to know if there is a Python library that can be used to convert GeoJSON Multi-polygon to a Polygon.

Note: i want to convert .geojson file Multi-Polygon feature type to Polygon feature type.

Best Answer

from osgeo import ogr

str = '''
{ "type": "MultiPolygon",
    "coordinates": [
        [
            [[40, 40], [20, 45], [45, 30], [40, 40]]
        ],
        [
            [[20, 35], [10, 30], [10, 10], [30, 5], [45, 20], [20, 35]],
            [[30, 20], [20, 15], [20, 25], [30, 20]]
        ]
    ]
}
'''
g = ogr.CreateGeometryFromJson(str) 

print "Hi! I'm a %s with an Area  %s" % (g.GetGeometryName(), g.Area())
print "I have inside me %s feature(s)!\n" % g.GetGeometryCount()
for idx, f in enumerate(g):
    print "I'm feature n.%s and I am a %s.\t I have an Area of %s - You can get my json repr with f.ExportToJson()" % (idx, f.GetGeometryName(),f.Area())

>>> Hi! I'm a MULTIPOLYGON with an Area 712.5
>>> I have inside me 2 feature(s)!

>>> I'm feature n.0 and I am a POLYGON. I have an Area of 87.5 - You can get my json repr with f.ExportToJson()
>>> I'm feature n.1 and I am a POLYGON. I have an Area of 625.0 - You can get my json repr with f.ExportToJson()

Related Solutions

[GIS] Converting GeoJSON to Shapefile using ogr2ogr

You have to force the SHP geometry type (because the geometry type of GeoJSON Geometry Collection is not supported in SHPs) and use the -skipfailures option:

ogr2ogr -nlt POINT -skipfailures points.shp geojsonfile.json OGRGeoJSON    
ogr2ogr -nlt LINESTRING -skipfailures linestrings.shp geojsonfile.json OGRGeoJSON
ogr2ogr -nlt POLYGON -skipfailures polygons.shp geojsonfile.json OGRGeoJSON

(Tested with GDAL 1.10.0, released 2013/04/24)

[GIS] C# / .NET library for converting GeoJson to KML

I couldn't find a library, but I coded up a solution that fit my requirements to handle polygons only. The code is provided below for anyone else who might find it useful. ConvertGeoJsonToKml generates complete KML and ConvertGeoJsonToKmlGeometryOnly generates a cut down KML output suitable for use in Google Fusion Tables.

using ArcGIS.ServiceModel.Common;
using ArcGIS.ServiceModel.GeoJson;
using Newtonsoft.Json;
using System;
using System.Linq;
using System.Xml.Linq;

namespace MyKickassProject.Utilities
{
    public static class GeometryUtils
    {
        public static string ConvertGeoJsonToKml(string geoJson)
        {
            SharpKml.Dom.Document kmlDocument = new SharpKml.Dom.Document();
            SharpKml.Dom.Placemark kmlPlacemark = new SharpKml.Dom.Placemark();

            kmlPlacemark.Geometry = GeneratePolygon(geoJson);

            kmlDocument.AddFeature(kmlPlacemark);

            SharpKml.Dom.Kml kml = new SharpKml.Dom.Kml();
            kml.Feature = kmlDocument;

            var serializer = new SharpKml.Base.Serializer();
            serializer.Serialize(kml);

            return serializer.Xml;
        }

        public static string ConvertGeoJsonToKmlGeometryOnly(string geoJson)
        {
            SharpKml.Dom.Polygon kmlPolygon = GeneratePolygon(geoJson);

            var serializer = new SharpKml.Base.Serializer();
            serializer.SerializeRaw(kmlPolygon);

            return RemoveAllNamespaces(serializer.Xml);
        }

        private static SharpKml.Dom.Polygon GeneratePolygon(string geoJson)
        {
            var polygon = JsonConvert.DeserializeObject<GeoJsonPolygon>(geoJson);

            if (polygon.Coordinates.Count > 0)
            {
                SharpKml.Dom.Polygon kmlPolygon = new SharpKml.Dom.Polygon();

                SharpKml.Dom.OuterBoundary kmlOuterBoundary = new SharpKml.Dom.OuterBoundary();
                kmlOuterBoundary.LinearRing = PointCollectionToLinearRing(polygon.Coordinates[0]);
                kmlPolygon.OuterBoundary = kmlOuterBoundary;

                if (polygon.Coordinates.Count > 1)
                {
                    for (int i = 1; i < polygon.Coordinates.Count; i++)
                    {
                        SharpKml.Dom.InnerBoundary kmlInnerBoundary = new SharpKml.Dom.InnerBoundary();
                        kmlInnerBoundary.LinearRing = PointCollectionToLinearRing(polygon.Coordinates[i]);
                        kmlPolygon.AddInnerBoundary(kmlInnerBoundary);
                    }
                }

                return kmlPolygon;
            }

            throw new Exception("GeoJSON type is unhandled.");
        }

        private static SharpKml.Dom.LinearRing PointCollectionToLinearRing(PointCollection coordinates)
        {
            var linearRing = new SharpKml.Dom.LinearRing();
            linearRing.Coordinates = new SharpKml.Dom.CoordinateCollection();
            var points = coordinates.AsEnumerable();
            foreach (var point in points)
            {
                linearRing.Coordinates.Add(new SharpKml.Base.Vector(point[1], point[0]));
            }
            return linearRing;
        }

        private static string RemoveAllNamespaces(string xmlDocument)
        {
            XElement xmlDocumentWithoutNs = RemoveAllNamespaces(XElement.Parse(xmlDocument));

            return xmlDocumentWithoutNs.ToString();
        }

        private static XElement RemoveAllNamespaces(XElement xmlDocument)
        {
            if (!xmlDocument.HasElements)
            {
                XElement xElement = new XElement(xmlDocument.Name.LocalName);
                xElement.Value = xmlDocument.Value;

                foreach (XAttribute attribute in xmlDocument.Attributes())
                    xElement.Add(attribute);

                return xElement;
            }
            return new XElement(xmlDocument.Name.LocalName, xmlDocument.Elements().Select(el => RemoveAllNamespaces(el)));
        }
    }
}

Best Answer

Related Solutions

[GIS] Converting GeoJSON to Shapefile using ogr2ogr

[GIS] C# / .NET library for converting GeoJson to KML

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