DjangoCon Europe 2019: Maps with GeoDjango, PostGIS and Leaflet

Writeup of the DjangoCon Europe 2019 talk »Maps with GeoDjango, PostGIS and Leaflet« by Paolo Melchiorre

Paolo Melchiorre: A Python developer who contributes to the Django project and gives talks at tech conferences.

Web map

Web maps are maps on websites, delivered by a GIS system. It can be static or interactive, and use raster or vector tiles. The data is stored in spatial databases, and then displayed using javascript

GeoDjango

django.contrib.gis provides a geographic framework with spatial field types, spatial ORM queries, Admin support, and support for four database backends.

PostGIS

PostGIS is the GIS backend for Postgres, and the most complete GeoDjango backend with spatial indexing and functions.

Leaflet

Leaflet is a JavaScript library for maps, smaller than 40kB of gzip'd JS, is desktop and mobile friendly, open source, and performs very well.

Usage

Install packages, and configure settings by adding django.contrib.gis to the installed apps, and the proper postgis as a database. Next up, generate an empty migration, and use the CreateExtension function to integrate PostGIS. You can also easily modify the admin to display a default location on the map for GIS fields.

from django.db import models
from django.contib.gis.db.models import PointField
from django.contib.gis.admin import OSMGeoAdmin

class Entry(models.Model)
    point = PointField()


@admin.register(Entry)
class EntryAdmin(OSMGeoAdmin):
    default_latitude = …

The JavaScript integration is easy to do with leaflet

var m = L.map('m').setView([x, y], zoomLevel);
L.tileLayer('//{s}.tile.osm.org/{z}/{x}/{y}.png').addTo(m);

Additional tooling

djangorestframework-gis provides GIS support to Django Rest Framework via a GeoFeatureModelSerializer and filtering with django-filter via InBBoxFilter.