Views

GeoJSON layer view

Very useful for web mapping :

# urls.py
from djgeojson.views import GeoJSONLayerView
...
url(r'^data.geojson$', GeoJSONLayerView.as_view(model=MushroomSpot), name='data'),

Consume the vector layer as usual, for example, with Leaflet loaded with jQuery Ajax:

# Leaflet JS
var layer = L.geoJson();
map.addLayer(layer);
$.getJSON("{% url 'data' %}", function (data) {
    layer.addData(data);
});

Inherit generic views only if you need a reusable set of options :

# views.py
from djgeojson.views import GeoJSONLayerView

class MapLayer(GeoJSONLayerView):
    # Options
    precision = 4   # float
    simplify = 0.5  # generalization


# urls.py
from .views import MapLayer, MeetingLayer
...
url(r'^mushrooms.geojson$', MapLayer.as_view(model=MushroomSpot, properties=('name',)), name='mushrooms')

Most common use-cases of reusable options are: low-fi precision, common list of fields between several views, etc.

Options are :

  • properties : list of properties names, or dict for mapping field names and properties
  • simplify : generalization of geometries (See simplify())
  • precision : number of digit after comma
  • geometry_field : name of geometry field (default: geom)
  • srid : projection (default: 4326, for WGS84)
  • bbox : Allows you to set your own bounding box on feature collection level
  • bbox_auto : True/False (default false). Will automatically generate a bounding box on a per feature level.
  • use_natural_keys : serialize natural keys instead of primary keys (default: False)

Tiled GeoJSON layer view

Vectorial tiles can help display a great number of objects on the map, with reasonnable performance.

# urls.py
from djgeojson.views import TiledGeoJSONLayerView
...

url(r'^data/(?P<z>\d+)/(?P<x>\d+)/(?P<y>\d+).geojson$',
    TiledGeoJSONLayerView.as_view(model=MushroomSpot), name='data'),

Consume the vector tiles using Leaflet TileLayer GeoJSON, Polymaps, OpenLayers 3 or d3.js for example.

Options are :

  • trim_to_boundary : if True geometries are trimmed to the tile boundary
  • simplifications : a dict of simplification values by zoom level

GeoJSON template filter

Mainly useful to dump features in HTML output and bypass AJAX call :

// Leaflet JS
L.geoJson({{ object_list|geojsonfeature|safe}}).addTo(map);

Will work either for a model, a geometry field or a queryset.

{% load geojson_tags %}

var feature = {{ object|geojsonfeature|safe }};

var geom = {{ object.geom|geojsonfeature|safe }};

var collection = {{ object_list|geojsonfeature|safe }};

Properties and custom geometry field name can be provided.

{{ object|geojsonfeature:"name,age" }}
{{ object|geojsonfeature:"name,age:the_geom" }}
{{ object|geojsonfeature:":geofield" }}