Export geoJSON data from Google Maps

Question

Is there built-in support or any library to export geoJSON data from the google.maps.Data layer or google.maps.Data.Feature or googl

Answer 1

A sample-function:

google.maps.Map.prototype.getGeoJson=function(callback){
  var geo={"type": "FeatureCollection","features": []},
      fx=function(g,t){

        var that  =[],
            arr,
            f     = {
                      MultiLineString :'LineString',
                      LineString      :'Point',
                      MultiPolygon    :'Polygon',
                      Polygon         :'LinearRing',
                      LinearRing      :'Point',
                      MultiPoint      :'Point'
                    };

        switch(t){
          case 'Point':
            g=(g.get)?g.get():g;
            return([g.lng(),g.lat()]);
            break;
          default:
            arr= g.getArray();
            for(var i=0;i<arr.length;++i){
              that.push(fx(arr[i],f[t]));
            }
            if( t=='LinearRing' 
                  &&
                that[0]!==that[that.length-1]){
              that.push([that[0][0],that[0][1]]);
            }
            return that;
        }
      };

  this.data.forEach(function(feature){
   var _feature     = {type:'Feature',properties:{}}
       _id          = feature.getId(),
       _geometry    = feature.getGeometry(),
       _type        =_geometry.getType(),
       _coordinates = fx(_geometry,_type);

       _feature.geometry={type:_type,coordinates:_coordinates};
       if(typeof _id==='string'){
        _feature.id=_id;
       }

       geo.features.push(_feature);
       feature.forEachProperty(function(v,k){
          _feature.properties[k]=v;
       });
  }); 
  if(typeof callback==='function'){
    callback(geo);
  }     
  return geo;
}

The function creates an object with the data. You may pass a callback as argument which will be executed with the object as argument.

Sample-call:

//map is the google.maps.Map-instance
map.getGeoJson(function(o){console.log(o)});

Demo: http://jsfiddle.net/doktormolle/5F88D/

Note: the Demo also stores circles, but circles are not supported in GeoJSON. As a workaround it stores circles as a POINT with a radius-property.

When a POINT with a radius-property will be loaded into the data-layer the demo hides the marker and creates a circle based on geometry and the radius-property instead.

---

<edit>: there is now a built-in method available for geoJSON-export: google.maps.Data.toGeoJson()

See Save Map Instance outside of Google Maps for an example

Answer 2

None of these worked for me. I figured out a way to export custom Polygons which may be useful for other shapes as well.

Here's the key export function:

function getPathArray(polygon) {
    return polygon.getPath().getArray().map(p => {
        return { lat: p.lat(), lng: p.lng() }
    })
}

Here's a full example:

function initMap() {
    var map = new google.maps.Map(document.getElementById('map'), {
        zoom: 5,
        center: { lat: 25.774, lng: -70.190 }, // bermuda triangle
    });

    const bermudaTriangle = new google.maps.Polygon({
        paths: [
            { lat: 25.774, lng: -80.190 },
            { lat: 18.466, lng: -66.118 },
            { lat: 32.321, lng: -64.757 },
        ],
        strokeColor: '#FF0000',
        strokeOpacity: 0.8,
        strokeWeight: 2,
        fillColor: '#FF0000',
        fillOpacity: 0.35,
        editable: true,
        draggable: false
    });
    bermudaTriangle.setMap(map);

    bermudaTriangle.getPaths().forEach(function (path, index) {
        google.maps.event.addListener(path, 'insert_at', function () {
            var data = getPathArray(bermudaTriangle)
            console.log(JSON.stringify(data))
        })

        google.maps.event.addListener(path, 'remove_at', function () {
            var data = getPathArray(bermudaTriangle)
            console.log(JSON.stringify(data))
        })

        google.maps.event.addListener(path, 'set_at', function () {
            var data = getPathArray(bermudaTriangle)
            console.log(JSON.stringify(data))
        })
    })

    google.maps.event.addListener(bermudaTriangle, 'dragend', function () {
        console.log("dragged")
    })
}

function getPathArray(polygon) {
    return polygon.getPath().getArray().map(p => {
        return { lat: p.lat(), lng: p.lng() }
    })
}

Then use the json that gets printed to the console and import it

bermudaTriangle.setPath(JSON.parse(myJson))

Answer 3

Hi i would like to share what I did to export geojson data from google maps to an html textarea.

This was my html view

     <article id="article3" style="">
        <div style="margin: 2px 0px 2px 0px;">
            <button onclick= "exportData()">Save</button>
        </div>
        <textarea id="geojson-input" placeholder="..." class="" style="height: 97%; width: 100%"></textarea>
    </article>

This was my javascript

     map.data.toGeoJson(function (data) {
                document.querySelector('#geojson-input').innerHTML = JSON.stringify(data);
            });

The function togeojson which is a function of map.data class, will get all data from the maps and return on object. To display that object on my textarea, I had to convert that object to a string by using JSON.stringify(data);

Hopes that will help!