GeoDjango and Friends
I gave a talk last night to the Portland Python User Group at Webtrends on the geospatial capabilities of the Django web application framework. In addition to showing off GeoDjango, I took their basic WorldBorders sample and extended it to provide a GeoJSON web service that OpenLayers could consume.
World_Borders Tutorial_Plus (Source Code)
I essentially took a render_to_geojson utility developed by my friend Dane Springmeyer and put together a quick and dirty GeoJSON web service. The output from this service is ready to be consumed by an OpenLayers GeoJSON protocol. I then combined that with the GeoExt ‘Feature Store In An Ext Grid’ example and gave it a nice OpenStreetMap base layer.
Here’s an excerpt from the GeoJSON web service:
{"srid": 900913,"crs": {"type": "link","properties": {"href": "http://spatialreference.org/ref/epsg/900913/","type": "proj4"}},"type": "FeatureCollection","features": [{"geometry": {"type": "MultiPolygon","coordinates": [[[[-9774223.6553460006,1955094.8610100001
Here's the web service view:
def borders(request):
borders_qs = WorldBorders.objects.filter(subregion=request.GET.get('subregion'))
return render_to_geojson(
borders_qs,
geom_attribute='geom',
mimetype = 'text/plain',
proj_transform=900913,
pretty_print=True
)
and here's the client feature store that I hooked to it:
// create feature store, binding it to the vector layer
store = new GeoExt.data.FeatureStore({
layer: vecLayer,
fields: [
{name: 'name', type: 'string'},
{name: 'area', type: 'float'},
{name: 'pop2005', type: 'float'}
],
proxy: new GeoExt.data.ProtocolProxy({
protocol: new OpenLayers.Protocol.HTTP({
url: "/world/borders/json?subregion=13",
format: new OpenLayers.Format.GeoJSON()
})
}),
autoLoad: true
});