Beginning a GeoDjango project

Category: /blog /django
Tags: django geodjango

Install postgis and extension. If you miss ‘postgis-scripts’, you might see an error message when create extension step.

sudo aptitude install postgis postgresql-9.3-postgis-scripts
# Geospatial libs
sudo aptitude install binutils libproj-dev gdal-bin

Create a PostgreSQL database, and make geo extension available

sudo -u postgres
  psql geodjango
  CREATE EXTENSION postgis
  createdb -T template_postgis -O webuser geodjango

Create a project

django-admin startproject geodjango

ESRI Shapefile

.shp: Holds the vector data for the world borders geometries.
.shx: Spatial index file for geometries stored in the .shp.
.dbf: Database file for holding non-geometric attribute data (e.g.,
      integer and character fields).
.prj: Contains the spatial reference information for the
      geographic data stored in the shapefile.

To check a layer summary info

ogrinfo -so -fields=YES TM_WORLD_BORDERS-0.3.shp TM_WORLD_BORDERS-0.3

Spatial Queries

>>> pnt_wkt = 'POINT(-95.3385 29.7245)'
>>> from world.models import WorldBorder
>>> qs = WorldBorder.objects.filter(mpoly__contains=pnt_wkt)
>>> qs
[<WorldBorder: United States>]


>>> from django.contrib.gis.geos import Point
>>> pnt = Point(12.4604, 43.9420)
>>> sm = WorldBorder.objects.get(mpoly__intersects=pnt)
>>> sm
<WorldBorder: San Marino>


>>> sm = WorldBorder.objects.get(name='San Marino')
>>> sm.mpoly
<MultiPolygon object at 0x24c6798>
>>> sm.mpoly.wkt # WKT
MULTIPOLYGON (((12.4157980000000006 43.9579540000000009,
12.4505540000000003 43.9797209999999978, ...
>>> sm.mpoly.wkb # WKB (as Python binary buffer)
<read-only buffer for 0x1fe2c70, size -1, offset 0 at 0x2564c40>
>>> sm.mpoly.geojson # GeoJSON (requires GDAL)
'{ "type": "MultiPolygon", "coordinates": [ [ [ [ 12.415798, 43.957954 ], [
12.450554, 43.979721 ], ...

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