Maps with Django - PWC2021

MAPS WITH DJANGO PAOLO MELCHIORRE ~ @pauloxnet

Paolo Melchiorre ~ @pauloxnet 2

Paolo Melchiorre ~ @pauloxnet @pauloxnet • CTO at 20tab •
Remote worker • Software engineer • Python developer • Django contributor Paolo Melchiorre 3

Paolo Melchiorre ~ @pauloxnet 1.883 m 0 km 27 km
0 km 4

Paolo Melchiorre ~ @pauloxnet • Static or Dynamic • Interactive
or view only • Raster or Vector tiles • Spatial databases • Javascript library Web maps features 5

Paolo Melchiorre ~ @pauloxnet 6 Web mapping “… process of
using the maps delivered by Geographic Information Systems (GIS) on the Internet …” — “Web mapping”, Wikipedia

Paolo Melchiorre ~ @pauloxnet django 7

Paolo Melchiorre ~ @pauloxnet 8 Requirements $ python3 --version Python
3.9.0+ $ python3 -m venv ~/.virtualenvs/mymap $ . ~/.virtualenvs/mymap/bin/activate $ python3 -m pip install django~=3.1

Paolo Melchiorre ~ @pauloxnet 9 Creating the ‘mymap’ project $
cd ~/projects $ django-admin startproject mymap mymap ├── manage.py └── mymap ├── asgi.py ├── __init__.py ├── settings.py ├── urls.py └── wsgi.py

Paolo Melchiorre ~ @pauloxnet 10 Creating the ‘markers’ app $
cd mymap $ django-admin startapp markers markers ├── admin.py ├── apps.py ├── __init__.py ├── migrations │ └── __init__.py ├── models.py ├── tests.py └── views.py

Paolo Melchiorre ~ @pauloxnet 11 Activating the ‘markers’ app #
mymap/settings.py INSTALLED_APPS = [ "django.contrib.admin", "django.contrib.auth", "django.contrib.contenttypes", "django.contrib.sessions", "django.contrib.messages", "django.contrib.staticfiles", "markers", ]

Paolo Melchiorre ~ @pauloxnet 12 Adding a template view #
markers/views.py from django.views.generic import TemplateView class MarkersMapView(TemplateView): template_name = "map.html"

Paolo Melchiorre ~ @pauloxnet 13 Adding the ‘map’ template  <!doctype html> <html lang="en"> <head> <title>Markers Map</title> <meta name="viewport" content="width=device-width, initial-scale=1.0"> </head> <body> </body> </html>

Paolo Melchiorre ~ @pauloxnet 14 Adding ‘markers’ urls # markers/urls.py
from django.urls import path from markers.views import MarkersMapView app_name = "markers" urlpatterns = [ path("map/", MarkersMapView.as_view()), ]

Paolo Melchiorre ~ @pauloxnet 15 Updating ‘mymap’ urls # mymap/urls.py
from django.contrib import admin from django.urls import include, path urlpatterns = [ path("admin/", admin.site.urls), path("markers/", include("markers.urls")), ]

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Paolo Melchiorre ~ @pauloxnet • JavaScript library for maps •
Free Software • Desktop & Mobile friendly • Light (~39 KB of gzipped JS) • Well documented Leaﬂet 17

Paolo Melchiorre ~ @pauloxnet 18 Updating the ‘map’ template  {% load static %} <!doctype html> <html lang="en"> <head> <title>Markers Map</title> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <link rel="stylesheet" type="text/css" href="{% static 'map.css' %}"> <link rel="stylesheet" type="text/css" href="//unpkg.com/leaflet/dist/leaflet.css"> <script src="//unpkg.com/leaflet/dist/leaflet.js"></script> </head> <body> <div id="map"></div> <script src="{% static 'map.js' %}"></script> </body> </html>

Paolo Melchiorre ~ @pauloxnet 19 Adding the ‘map’ CSS /*
markers/static/map.css */ html, body { height: 100%; margin: 0; } #map { height: 100%; width: 100%; }

Paolo Melchiorre ~ @pauloxnet 20 Adding the ‘map’ JavaScript //
markers/static/map.js const copy = '© <a href="https://osm.org/copyright">OpenStreetMap</a> contributors' const url = 'https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png' const osm = L.tileLayer(url, { attribution: copy }) const map = L.map('map', { layers: [osm] }) map.fitWorld();

Paolo Melchiorre ~ @pauloxnet 21 Show the empty web map
$ python3 manage.py runserver $ python3 -m webbrowser -t localhost:8000/markers/map

6 km 23

Paolo Melchiorre ~ @pauloxnet 24 GeoDjango django.contrib.gis (v1.0 ~2008) Fields,
backends, queries, admin, … Spatialite backend (v1.1 ~2009) Multiple backends (v1.2 ~2010) OpenLayers-based widgets (v1.6 ~2013) GeoJSON serializer (v1.8 ~2015) GeoIP2 Geolocation (v1.9 ~2016)

Paolo Melchiorre ~ @pauloxnet • OSGeo library • Free Software
• Read/Write geospatial data • Raster/Vector formats • Command line interface GDAL 25

Paolo Melchiorre ~ @pauloxnet 26 Installing GDAL # apt-get install
gdal-bin # # -- Read the docs for other operating systems.

Paolo Melchiorre ~ @pauloxnet 27 Activating GeoDjango # mymap/settings.py INSTALLED_APPS
= [ "django.contrib.admin", "django.contrib.auth", "django.contrib.contenttypes", "django.contrib.sessions", "django.contrib.messages", "django.contrib.staticfiles", "django.contrib.gis", "markers", ]

Paolo Melchiorre ~ @pauloxnet • SQLite spatial extension • Vector
geodatabase functions • Free Software • Simple architecture • Single ﬁle SpatiaLite 28

Paolo Melchiorre ~ @pauloxnet 29 Installing SpatiaLite # apt-get install
libsqlite3-mod-spatialite # # -- Read the docs for other operating systems.

Paolo Melchiorre ~ @pauloxnet 30 Activating SpatiaLite # mymap/settings.py DATABASES
= { "default": { "ENGINE": "django.contrib.gis.db.backends.spatialite", "NAME": BASE_DIR / "db.sqlite3", } }

Paolo Melchiorre ~ @pauloxnet 31 Adding the Marker model #
markers/models.py from django.contrib.gis.db import models class Marker(models.Model): name = models.CharField(max_length=255) location = models.PointField() def __str__(self): return self.name

Paolo Melchiorre ~ @pauloxnet 32 Adding the Marker admin #
markers/admin.py from django.contrib.gis import admin from markers.models import Marker @admin.register(Marker) class MarkerAdmin(admin.OSMGeoAdmin): list_display = ("name", "location")

Paolo Melchiorre ~ @pauloxnet 33 Adding some markers $ python3
manage.py makemigrations $ python3 manage.py migrate $ python3 manage.py createsuperuser $ python3 manage.py runserver $ python3 -m webbrowser -t localhost:8000/admin

Paolo Melchiorre ~ @pauloxnet 35 Updating the view # markers/views.py
import json from django.core.serializers import serialize from django.views.generic.base import TemplateView from markers.models import Marker class MarkersMapView(TemplateView): template_name = "map.html" def get_context_data(self, **kwargs): context = super().get_context_data(**kwargs) markers = Marker.objects.all() context["markers"] = json.loads(serialize("geojson", markers)) return context

Paolo Melchiorre ~ @pauloxnet 36 Inserting markers in the template
 {% load static %} <!doctype html> <html lang="en"> <head> <title>Markers Map</title> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <link rel="stylesheet" type="text/css" href="{% static 'map.css' %}"> <link rel="stylesheet" type="text/css" href="//unpkg.com/leaflet/dist/leaflet.css"> <script src="//unpkg.com/leaflet/dist/leaflet.js"></script> </head> <body> {{ markers|json_script:"markers-data" }} <div id="map"></div> <script src="{% static 'map.js' %}"></script> </body> </html>

Paolo Melchiorre ~ @pauloxnet 37 Generated GeoJSON <script id="markers-data" type="application/json">
{ "type": "FeatureCollection", "crs": { "type": "name", "properties": { "name": "EPSG:4326" } }, "features": [ { "type": "Feature", "properties": { "name": "Monte Amaro 2793m", "pk": "1" }, "geometry": { "type": "Point", "coordinates": [14.08591836494682, 42.08632592463349] } } ] } </script>

Paolo Melchiorre ~ @pauloxnet 38 Rendering all markers in the
map // markers/static/map.js const copy = '© <a href="https://osm.org/copyright">OpenStreetMap</a> contributors' const url = 'https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png' const osm = L.tileLayer(url, { attribution: copy }) const map = L.map('map', { layers: [osm], minZoom: 5 }) const markers = JSON.parse(document.getElementById('markers-data').textContent) const features = L.geoJSON(markers).bindPopup(layer => layer.feature.properties.name) map.addLayer(features).fitBounds(feature.getBounds())

Paolo Melchiorre ~ @pauloxnet 39 Show the populated web map
$ python3 manage.py runserver $ python3 -m webbrowser -t localhost:8000/markers/map

7 km 41

Paolo Melchiorre ~ @pauloxnet • PostgreSQL extension • Best* GeoDjango
backend • Spatial data types • Spatial indexing • Spatial functions PostGIS 42

Paolo Melchiorre ~ @pauloxnet 43 Installing PostgreSQL C client library
# apt-get install libpq5 # # -- Read the docs for other operating systems.

Paolo Melchiorre ~ @pauloxnet 44 Activating PostGIS # mymap/settings.py DATABASES
= { "default": { "ENGINE": "django.contrib.gis.db.backends.postgis", "HOST": "database", "NAME": "mymap", "PASSWORD": "password", "PORT": 5432, "USER": "postgres", } }

Paolo Melchiorre ~ @pauloxnet 45 Requirements # requirements.txt django~=3.1.0 psycopg2~=2.8.0
djangorestframework~=3.12.0 djangorestframework-gis~=0.17 django-filter~=2.4.0

Paolo Melchiorre ~ @pauloxnet 46 Installing requirements $ python3 -m
pip install -r requirements.txt

Paolo Melchiorre ~ @pauloxnet 47 Activating Django REST Framework #
mymap/settings.py INSTALLED_APPS = [ "django.contrib.admin", "django.contrib.auth", "django.contrib.contenttypes", "django.contrib.sessions", "django.contrib.messages", "django.contrib.staticfiles", "django.contrib.gis", "rest_framework", "rest_framework_gis", "markers", ]

Paolo Melchiorre ~ @pauloxnet 48 Adding the Marker serializer #
markers/serializers.py from rest_framework_gis import serializers from markers.models import Marker class MarkerSerializer(serializers.GeoFeatureModelSerializer): class Meta: fields = ("id", "name") geo_field = "location" model = Marker

Paolo Melchiorre ~ @pauloxnet 49 Adding the Marker viewset #
markers/api_views.py from rest_framework import viewsets from rest_framework_gis import filters from markers.models import Marker from markers.serializers import MarkerSerializer class MarkerViewSet(viewsets.ReadOnlyModelViewSet): bbox_filter_field = "location" filter_backends = (filters.InBBoxFilter,) queryset = Marker.objects.all() serializer_class = MarkerSerializer

Paolo Melchiorre ~ @pauloxnet 50 Adding API ‘markers’ urls #
markers/api_urls.py from rest_framework import viewsets from rest_framework import routers from markers.api_views import MarkerViewSet router = routers.DefaultRouter() router.register(r"markers", MarkerViewSet) urlpatterns = router.urls

Paolo Melchiorre ~ @pauloxnet 51 Updating ‘mymap’ urls # mymap/urls.py
from django.contrib import admin from django.urls import include, path urlpatterns = [ path("admin/", admin.site.urls), path("api/", include("markers.api_urls")), path("markers/", include("markers.urls")), ]

Paolo Melchiorre ~ @pauloxnet 52 Trying to locate the user
// markers/static/map.js const copy = '© <a href="https://osm.org/copyright">OpenStreetMap</a> contributors' const url = 'https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png' const osm = L.tileLayer(url, { attribution: copy }) const map = L.map('map', { layers: [osm], minZoom: 5 }) map.locate() .on('locationfound', e => map.setView(e.latlng, 8)) .on('locationerror', () => map.setView([0, 0], 5)) // …

Paolo Melchiorre ~ @pauloxnet 53 Rendering markers incrementally // markers/static/map.js
async function load_markers() { const markers_url = `/api/markers/?in_bbox=${map.getBounds().toBBoxString()}` const response = await fetch(markers_url) const geojson = await response.json() return geojson } async function render_markers() { const markers = await load_markers() L.geoJSON(markers).bindPopup(layer => layer.feature.properties.name).addTo(map) } map.on('moveend', render_markers)

14 km 55

Paolo Melchiorre ~ @pauloxnet 56 What’s next • Markers customization
• Relational ﬁltering • Clustering frontend/backend • Geocoding services • …

Paolo Melchiorre ~ @pauloxnet 57 Tips • docs in djangoproject.com
• details in postgis.net • source code in github.com • questions in gis.stackexchange.com

Paolo Melchiorre ~ @pauloxnet 58 License CC BY-SA 4.0 This
work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

Paolo Melchiorre ~ @pauloxnet @20tab 20tab 20tab [email protected] 20tab.com 59

Paolo Melchiorre ~ @pauloxnet @pauloxnet paolomelchiorre pauloxnet [email protected] paulox.net 60

Maps with Django - PWC2021

Maps with Django - PWC2021

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