Geojson to Topojson in node.js

Question

I have a shape file in my postGIS database.I have retrieved that into geojson in node.js by using the following code.

var moisql = 'SELECT *, (ST_AsGeoJSON(geom))  from xxx;'

Works fine..But my requirement is i have to convert this geojson file into "TOPOJSON".

SO i have this code:

topojsonOutput = topojson.topology({'collection': geojsonString});

But still i am retrieving geojson file as output..SO please guide me to achieve this..Thanks in advance.

Also when i googled i got this code:

var collection = {type: "FeatureCollection", features: […]}; // GeoJSON
var topology = topojson.topology({collection: collection}); // convert to TopoJSON
console.log(topology.objects.collection); // inspect TopoJSON

But totally i can't understand this..What i have to give in place of features[..] and collections..

score 2 · Answer 1 · answered Dec 27 '13 at 05:15

2

There's a PostGIS AsTopoJSON function available for PostGIS 2.1.0 and greater. Alternatively, there's the postgis2geojson conversion tool; you might want to look at how it wraps the snippets that ST_AsGeoJSON returns.

answered Dec 27 '13 at 05:15

banderkat

481
2
6

score 0 · Answer 2 · answered Dec 26 '13 at 05:53

Taken from example here.

var topology = topojson.topology({
        collection: {
          type: "FeatureCollection",
          features: [
            {type: "Feature", geometry: {type: "LineString", coordinates: [[.1, .2], [.3, .4]]}},
            {type: "Feature", geometry: {type: "Polygon", coordinates: [[[.5, .6], [.7, .8]]]}}
          ]
        }
      });

Geojson to Topojson in node.js

2 Answers2