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GDAL PostGIS Raster driver documentation
Last update: December 2012
Note for users: The first GDAL stable version to include the last bug fixes will be GDAL 1.10, due to 2012/12/31. Until then, use the nightly snapshots (http://www.gdal.org/daily) or the last version from trunk (https://svn.osgeo.org/gdal/trunk/gdal)
Note for developers: There is a open discussion on GDAL driver design at PostGIS Raster wiki
1 - Introduction
PostGIS Raster (previously known as WKT Raster) is the project that provides raster support on PostGIS. Since September 26st, 2010, is an official part of PostGIS project. Further information here.
This driver was started during the Google Summer of Code 2009, and improved since then, being under development at same time than PostGIS Raster extension itself. So far, this is a read-only driver. The next version of the driver will include these features:
- Out-db raster support.
- Create and modify raster on PostGIS database.
Please, use GDAL 2.0 from trunk (until the official release of GDAL 2.0). The driver packed with previous GDAL versions was buggy and unstable, and it won't work with the last versions of PostGIS Raster (since it was included in PostGIS trunk).
Take into account that:
- GDAL doesn't require PostgreSQL/PostGIS installed in your machine to work. But...
- PostGIS 2.0 (the version of PostGIS that includes PostGIS Raster) DOES require GDAL.
So, if you want to use GDAL PostGIS Raster driver:
- ALWAYS use GDAL version 2.0 from trunk or higher.
- Apart from this, if you want to use the driver against your own PostGIS version, use PostGIS 2.0
1.1 - Credits
Development
- Jorge Arévalo (jorgearevalo at libregis.org)
- David Zwarg (dzwarg at azavea.com)
1.2 - More information
- PostGIS Raster documentation page here
- Introduction to PostGIS Raster format and description of the work done during the Google Summer of Code 2009 here
- Search for "WKT Raster" in the PostGIS-users and PostGIS-devel forums archives or in Nabble or write to these forums.
2 - Installation
2.1 - Installing prerequisites
You don't need special requisites in your machine for using GDAL driver, apart from GDAL library itself. Anyway, you might want to set an enviroment with PostgreSQL/PostGIS/PostGIS Raster support. In that case, you'll need:
- PostgreSQL version 8.3 or higher
- Proj4 library version 4.5.0 or higher
- GEOS library version 3.1.0 or higher
- Python version 2.5 or higher
- PostGIS versión 2.0 or higher
NOTE: PostGIS 2.0 has not a stable candidate yet (March 2012). So, you'll have to download and install the lastest development snapshot. Don't use any PostGIS version below 2.0.
Linux users can install PostGIS 2.0 following the classical ./configure & make & make install way. Windows users can follow these instructions. Mac user can consult William Kyngesburye instructions
2.2 - Installing GDAL
2.2.1 - From binaries
You can find GDAL binaries for Linux/Windows/Mac at GDAL download page. Please, until the official release of GDAL 2.0, use the binaries compiled from development version.
2.2.2 - From sources
You can download daily GDAL snapshots from here, or checkout the code directly from SVN with any subversion client. The examples of this documentation are using Linux console client, but they're easily reproducible with any other client, simply using the same URLs
>$ svn checkout https://svn.osgeo.org/gdal/trunk/gdal gdal
After that, you have to build GDAL library with Python support:
>$ ./configure --with-python & make & make install
Further instructions here.
3 - Using GDAL PostGIS Raster driver
3.1 - Loading raster data in the database
The GDAL PostGIS Raster driver does not support writing raster to the database yet. But you can load raster data in the database in 2 ways:
The write support to GDAL PostGIS Raster driver is under development.
3.2 - Reading raster data from the database
If you want to use the GDAL WKT Raster driver, you must provide a connection string as Dataset's name. The syntax of this connection string is (the quotes may be ommitted):
PG":host='<host>' port:'<port>' dbname='<dbname>' user='<user>' password='<password>' [schema='<schema>'] [table='<raster_table>'] [where='<sql_where>'] [mode='<working_mode>']"
Note that the string, up to the part starting with "table='" is a libpq-style connection string. That means that you can leave out unnecessary fields (like password, in some cases).
The "table" option requires the name of a PostGIS Raster table. This table was created when the roaster was loaded.
The "where" option is used to filter the results of the raster table. Any SQL-WHERE expression is valid. The "mode" option is used to know the expected arrangement of the raster table. There are 2 possible values:
- mode = 1. Also called ONE_RASTER_PER_ROW mode. In this case, a raster table is considered as a bunch of different raster files. This mode is intended for raster tables storing different raster files. It's the default mode if you don't provide this field in connection string.
- mode = 2. Also called ONE_RASTER_PER_TABLE mode. In this case, a raster table is considered as a unique raster file, even if the table has more than one row. This mode is intended for reading tiled rasters from database.
Three important notes here:
- If a table stores a tiled raster and you execute the driver with mode = 1, each image tile will be considered as a different image, and will be reported as a subdataset.
- There are use cases the driver can't still work with. For example: non-regular blocked rasters. That cases are detected and an error is raised. Anyway, as I've said, the driver is under development, and will work with more raster arrangements ASAP.
- There's an additional working mode. If you don't provide a table name, the driver will look for existing raster tables in all allowed database' schemas, and will report each table as a subdataset.
You must use this connection string's format in all the gdal tools, like gdalinfo, gdal_translate, gdalwarp, etc.
To see examples, check the PostGIS Raster FAQ section: Can I export my PostGIS Raster data to other raster formats?
3.3 - Creating and modifying data
The GDAL PostGIS Raster driver does not support creation and edition of rasters yet. Check the section 3.1, to know how to load raster data in the database.
4 - Reporting problems
To report errors and suggestions, use New Ticket form of this Trac system or you can use the gdal-dev list or write an e-mail to:
- Jorge Arévalo: jorgearevalo at libregis.org
- David Zwarg: dzwarg at azavea.com
When reporting here on the Trac, please specify the the PostGISRaster driver name in the keywords field.
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