Installing GeoDjango and PostgreSQL with PostGIS

This is our final installation recipe and if you have followed along so far, you are ready for a simple, straightforward start to Django. Django is a web framework for professionals with deadlines, according to the Django homepage. The spatial part of it can be found in GeoDjango. GeoDjango is a contrib module installed with every Django installation therefore, you only need to install Django to get GeoDjango running. Of course, "geo" has its dependencies that were met in the previous sections. For reference purposes, take a look at this great documentation on the Django homepage at

https://docs.djangoproject.com/en/dev/ref/contrib/gis/install/#ref-gis-install.

We will use PostgreSQL and PostGIS since they are the open source industry go-to spatial databases. The installations are not 100% necessary, but without them there is no real point because you then limit your operations, and they're definitely needed if you plan to store your spatial data in a spatial database. The combination of PostgreSQL and PostGIS is the most common spatial database setup for GeoDjango. This installation is definitely more involved and can lead to some hook-ups depending on your system.

Getting ready

To use GeoDjango, we will need to have a spatial database installed, and in our case, we will be using PostgreSQL with the PostGIS extension. GeoDjango also supports Oracle, Spatialite, and MySQL. The dependencies of PostGIS include GDAL, GEOS, PROJ.4, LibXML2, and JSON-C.

Start up your Python virtual environment as follows:

mdiener@mdiener-VirtualBox:~$ workon pygeoan_cb
(pygeoan_cb)mdiener@mdiener-VirtualBox:~$

Tip

Downloading the example code

You can download the example code files for all Packt books you have purchased from your account at http://www.packtpub.com. If you purchased this book elsewhere, you can visit http://www.packtpub.com/support and register to have the files e-mailed directly to you.

How to do it...

Follow these steps. These are taken from the PostgreSQL homepage for Ubuntu Linux:

1. Create a new file called pgdg.list using the standard gedit text editor. This stores the command to fire up your Ubuntu installer package:

   $ sudo gedit /etc/apt/sources.list.d/pgdg.list
   

2. Add this line to the file, save, and then close it:

   $ deb http://apt.postgresql.org/pub/repos/apt/ precise-pgdg main
   

3. Now, run the wget command for add the key:

   $ wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | \ sudo apt-key add -
   

4. Run the update command to actualize your installer packages:

   $ sudo apt-get update
   

5. Run the install command to actually install PostgreSQL 9.3:

   $ sudo apt-get install postgresql-9.3
   

6. To install PostGIS 2.1, we will have one unmet dependency, libgdal1, so go ahead and install it:

   $ sudo apt-get install libgdal1
   

7. Now we can install PostGIS 2.1 for PostgreSQL 9.3 on our machine:

   $ sudo apt-get install postgresql-9.3-postgis-2.1
   

8. Install the PostgreSQL header files:

   $ sudo apt-get install libpq-dev
   

9. Finally, install the contrib module with contributions:

   $ sudo apt-get install postgresql-contrib
   

10. Install the Python database adapter, psycopg2, to connect to your PostgreSQL database from Python:

    $ sudo apt-get install python-psycopg2
    

11. Now we can create a standard PostgreSQL database as follows:

    (pygeoan_cb)mdiener@mdiener-VirtualBox:~$ createdb [NewDatabaseName]
    

12. Using the psql command-line tool, we can create a PostGIS extension to our newly created database to give it all the PostGIS functions as follows:

    (pygeoan_cb)mdiener@mdiener-VirtualBox:~$ psql -d [NewDatabaseName] -c "CREATE EXTENSION postgis;"
    

13. Moving on, we can finally install Django in one line directly in our activated virtual environment:

    $ pip install django
    

14. Test out your install of Django and GDAL and, as always, try to import them as follows:

    >>> from django.contrib.gis import gdal
    >>> gdal.HAS_GDAL
    True
    

Windows users should be directed to the PostgreSQL Windows (http://www.postgresql.org/download/windows/) binaries provided by EnterpriseDB (http://www.enterprisedb.com/products-services-training/pgdownload#windows). Download the correct version and follow the installer instructions. PostGIS is also included in the list of extensions that you can directly install using the installer.

How it works...

Installations using the apt-get Ubuntu installer and the Windows installers are simple enough in order to have PostgreSQL, PostGIS, and Django up and running. However, the inner workings of the installers are beyond the scope of this book.

There's more...

To summarize all the installed libraries, take a look at this table:

Library name	Description	Reason to install
NumPy	This adds support for large multidimensional arrays and matrices	It is a requirement for many other libraries
pyproj	This handles projections	It transforms projections
shapely	This handles geospatial operations	It performs fast geometry manipulations and operations
matplotlib	This plots libraries	It provides a quick visualization of results
descartes	This uses Shapely or GeoJSON objects as matplotlib paths and patches	It speedily plots geo-data
pandas	This provides high-performance data structures and data analysis	It performs data manipulation, CSV creation, and data manipulation
SciPy	This provides a collection of Python libraries for scientific computing	It has the best collection of necessary tools
PySAL	This contains a geospatial analysis library	It performs a plethora of spatial operations (optional)
IPython	This provides interactive Python computing	It is a helpful notebook to store and save your scripts (optional)
Django	This contains a web application framework	It is used for our demo web application in Chapter 11, Web Analysis with GeoDjango
pyshp	This provides pure Python shapefile manipulation and generation	It helps input and output shapefiles
GeoJSON	This contains the JSON format for spatial data	It facilitates the exchange and publication of this format
PostgreSQL	This is a relational database	It helps store spatial data
PostGIS	This is the spatial extension to PostgreSQL	It stores and performs spatial operations on geographic data in PostgreSQL