# Τεκμηρίωση του Django - 1.10.7

# Installing Geospatial libraries

GeoDjango uses and/or provides interfaces for the following open source geospatial libraries:

Program | Description | Required | Supported Versions
--- | --- | --- | ---
GEOS | Geometry Engine Open Source | Yes | 3.4, 3.3
PROJ.4 | Cartographic Projections library | Yes (PostgreSQL and SQLite only) | 4.9, 4.8, 4.7, 4.6, 4.5, 4.4
GDAL | Geospatial Data Abstraction Library | Yes (SQLite only) | 2.1, 2.0, 1.11, 1.10, 1.9, 1.8, 1.7
GeoIP | IP-based geolocation library | No | 2
PostGIS | Spatial extensions for PostgreSQL | Yes (PostgreSQL only) | 2.3, 2.2, 2.1, 2.0
SpatiaLite | Spatial extensions for SQLite | Yes (SQLite only) | 4.3, 4.2, 4.1, 4.0, 3.0

Note that older or more recent versions of these libraries may also work totally fine with GeoDjango. Your mileage may vary.

Install GDAL

While GDAL is technically not required, it is recommended. Important features of GeoDjango (including the LayerMapping data import utility, geometry reprojection, and the geographic admin) depend on its functionality.

Σημείωση

The GeoDjango interfaces to GEOS, GDAL, and GeoIP may be used independently of Django. In other words, no database or settings file required – just import them as normal from `django.contrib.gis`.

On Debian/Ubuntu, you are advised to install the following packages which will install, directly or by dependency, the required geospatial libraries:

    $ sudo apt-get install binutils libproj-dev gdal-bin

Optional packages to consider:

- `libgeoip1`: for GeoIP support
- `python-gdal` for GDAL’s own Python bindings – includes interfaces for raster manipulation

Please also consult platform-specific instructions if you are on Mac OS X or Windows.

## Building from source

When installing from source on UNIX and GNU/Linux systems, please follow the installation instructions carefully, and install the libraries in the given order. If using MySQL or Oracle as the spatial database, only GEOS is required.

Σημείωση

On Linux platforms, it may be necessary to run the `ldconfig` command after installing each library. For example:

    $ sudo make install
    $ sudo ldconfig

Σημείωση

OS X users are required to install Apple Developer Tools in order to compile software from source. This is typically included on your OS X installation DVDs.

### GEOS

GEOS is a C++ library for performing geometric operations, and is the default internal geometry representation used by GeoDjango (it’s behind the “lazy” geometries). Specifically, the C API library is called (e.g., `libgeos_c.so`) directly from Python using ctypes.

First, download GEOS 3.4.2 from the GEOS website and untar the source archive:

    $ wget http://download.osgeo.org/geos/geos-3.4.2.tar.bz2
    $ tar xjf geos-3.4.2.tar.bz2

Next, change into the directory where GEOS was unpacked, run the configure script, compile, and install:

    $ cd geos-3.4.2
    $ ./configure
    $ make
    $ sudo make install
    $ cd ..

#### Troubleshooting

##### Can’t find GEOS library

When GeoDjango can’t find GEOS, this error is raised:

    ImportError: Could not find the GEOS library (tried "geos_c"). Try setting GEOS_LIBRARY_PATH in your settings.

The most common solution is to properly configure your Library environment settings or set GEOS_LIBRARY_PATH in your settings.

If using a binary package of GEOS (e.g., on Ubuntu), you may need to Install binutils.

##### `GEOS_LIBRARY_PATH`

If your GEOS library is in a non-standard location, or you don’t want to modify the system’s library path then the `GEOS_LIBRARY_PATH` setting may be added to your Django settings file with the full path to the GEOS C library. For example:

    GEOS_LIBRARY_PATH = '/home/bob/local/lib/libgeos_c.so'

Σημείωση

The setting must be the full path to the C shared library; in other words you want to use `libgeos_c.so`, not `libgeos.so`.

See also My logs are filled with GEOS-related errors.

### PROJ.4

PROJ.4 is a library for converting geospatial data to different coordinate reference systems.

First, download the PROJ.4 source code and datum shifting files [1]:

    $ wget http://download.osgeo.org/proj/proj-4.9.1.tar.gz
    $ wget http://download.osgeo.org/proj/proj-datumgrid-1.5.tar.gz

Next, untar the source code archive, and extract the datum shifting files in the `nad` subdirectory. This must be done prior to configuration:

    $ tar xzf proj-4.9.1.tar.gz
    $ cd proj-4.9.1/nad
    $ tar xzf ../../proj-datumgrid-1.5.tar.gz
    $ cd ..

Finally, configure, make and install PROJ.4:

    $ ./configure
    $ make
    $ sudo make install
    $ cd ..

### GDAL

GDAL is an excellent open source geospatial library that has support for reading most vector and raster spatial data formats. Currently, GeoDjango only supports GDAL’s vector data capabilities [2]. GEOS and PROJ.4 should be installed prior to building GDAL.

First download the latest GDAL release version and untar the archive:

    $ wget http://download.osgeo.org/gdal/1.11.2/gdal-1.11.2.tar.gz
    $ tar xzf gdal-1.11.2.tar.gz
    $ cd gdal-1.11.2

Configure, make and install:

    $ ./configure
    $ make # Go get some coffee, this takes a while.
    $ sudo make install
    $ cd ..

Σημείωση

Because GeoDjango has its own Python interface, the preceding instructions do not build GDAL’s own Python bindings. The bindings may be built by adding the `--with-python` flag when running `configure`. See GDAL/OGR In Python for more information on GDAL’s bindings.

If you have any problems, please see the troubleshooting section below for suggestions and solutions.

#### Troubleshooting

##### Can’t find GDAL library

When GeoDjango can’t find the GDAL library, the `HAS_GDAL` flag will be false:

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

The solution is to properly configure your Library environment settings or set GDAL_LIBRARY_PATH in your settings.

##### `GDAL_LIBRARY_PATH`

If your GDAL library is in a non-standard location, or you don’t want to modify the system’s library path then the `GDAL_LIBRARY_PATH` setting may be added to your Django settings file with the full path to the GDAL library. For example:

    GDAL_LIBRARY_PATH = '/home/sue/local/lib/libgdal.so'

Footnotes

[1] | The datum shifting files are needed for converting data to and from certain projections. For example, the PROJ.4 string for the Google projection (900913 or 3857) requires the `null` grid file only included in the extra datum shifting files. It is easier to install the shifting files now, then to have debug a problem caused by their absence later.

[2] | Specifically, GeoDjango provides support for the OGR library, a component of GDAL.