Presentation at September 2011 Lambda Lounge.

1. GeoDjango &
HTML5 Geolocation
John Paulett john@paulett.org
September 1, 2011 @johnpaulett

3. The Plan
HTML5 Geolocation
Django Crash Course
What is GeoDjango?
GeoDjango Basics
Demo Application

4. Geolocation

5. W3C Geolocation
GPS, nearby Wi-Fi networks, cell towers, IP
address
IE 9, FF 3.6, Safari 5.0, Chrome, Opera 10.6, iOS,
Android
navigator.geolocation.getCurrentPosition
navigator.geolocation.watchPosition

6. W3C Geolocation
function showMap(position) {
console.log(position);
}
navigator.geolocation.getCurrentPosition(
showMap
);

7. W3C Geolocation
{
"coords": {
"accuracy": 22000,
"altitude": null,
"altitudeAccuracy": null,
"heading": null,
"latitude": 38.631756,
"longitude": -90.24323,
"speed": null
},
"timestamp": 1314459776275
}

8. Crash Course

9. models.py
from django.db import models
class City(models.Model):
name = models.TextField()
class UserGroup(models.Model):
name = models.TextField()
city = models.ForeignKey(City)
started = models.DateField()
def join(self, user):
# add user to group

10. urls.py
urlpatterns = patterns(
url(
r'^user-groups/(?P<city_name>w+)$',
'myapp.views.user_groups'
),
)

11. views.py
def user_groups(request, city_name):
city = City.objects.get(name=city_name)
groups = UserGroup.objects.filter(city=city)
return render(request, 'user_groups.html',
{'groups': groups})

12. user_groups.html
{% extends "base.html%}
<ul>
{% for group in groups %}
<li>
{{ group.name }}
</li>
{% endfor %}
</ul>

14. What is GeoDjango?
“world-class geographic Web framework”
included in Django core
Combine existing Python & DB tools with
standard API
but first …

15. Some GIS Problems
The Earth is not a sphere!
How to store & query efficiently
Vendor implementations
Wide range of data formats
Tiger/LINE, Shapefiles, E00, OGR, GeoJSON,
WKT, EWKT, EWKB, GML, KML, OSM, GLOBE,
TIFF, ArcGrid ….

16. GeoDjango Basics

17. GeoDjango Model Fields
from django.contrib.gis.db import models
models.PointField
models.LineStringField
models.PolygonField
models.MultiPointField
models.MultiLineStringField
models.MultiPolygonField
models.GeometryCollectionField

18. Given a Set of Geo Objects
Measure & Find:
distance, area, perimeter, centroid, envelope
Edit:
transform (SRID), scale
Operations:
intersection, difference, union
Output:
geojson, gml, kml, svg
SalesRegion.objects.all().kml()

19. Geo Querying
contains, covers, crosses, disjoint, equals,
intersects, touches, left/right, distance_lt,
distance_gt …
SalesRegion.objects.filter(
poly__distance_lt=(pnt, D(mi=500))
)

20. lambdageo

21. lambdageo
http://lambdageo.ep.io
http://github.com/johnpaulett/lambdageo

22. lambdageo.ep.io
●
models.py
Admin
Views
Templates

23. Django Admin

24. GIS is Cool
Python GIS
Tile Servers, Mapnik, etc.
Data
Openstreet Maps, Census

25. lambdageo.ep.io
github.com/johnpaulett/lambdageo
john@paulett.org / @johnpaulett

26. References

27. References
Python Geospatial Development – Erik
Westra

28. References
http://geodjango.org/
http://dev.w3.org/geo/api/spec-source.html
http://src.chromium.org/viewvc/chrome/tru
nk/src/chrome/browser/geolocation/
http://caniuse.com/#search=geolocation