Difference between revisions of "GDAL"

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==Installation==
 
==Installation==
Best install using standard system package manager, such as apt-get (Ubuntu), yum (Fedora), or macports (OSX).
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Best install using standard system package manager, such as apt-get (Ubuntu), yum (Fedora), or [https://www.macports.org/ macports] (OSX).
  
 
==Download==
 
==Download==
Downloading GDAL is very confusing. Web searches lead to dead links or irrelevant redirects. Documentation is nowhere to be found. The sofware installs without man pages. Typing gdal utilities from the command line with -help does produces nothing useful. But following works:
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The current download page is http://download.osgeo.org/gdal/. However, web searches for the code or documentation lead to many dead links to defuncts sites. In particular, almost all links leading inside https://gdal.org/ from internet search engines are dead.
* Download the appropriate version of sources from http://download.osgeo.org/gdal/ as tar.gz file
 
* expand the file
 
* install doxygen if needed, and type doxygen in the top directory of the source
 
* open file html/index.html
 
  
 
==Documentation==
 
==Documentation==
* Some apparently legacy documentation is at https://trac.osgeo.org/gdal/wiki which appears to be legacy but as far as I can tell it is actually the current one, and also leads to another download page.
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* Web searches for "gdal documentation" are futile, but there is index to just that at https://gdal.org and wiki https://trac.osgeo.org/gdal/wiki, which also links to alternative download pages. But that wiki seems old, there is a new wiki at https://wiki.osgeo.org/wiki/Main_Page.
* The documentation for version 2.4.0 was installed as described above [http://demo.openwfm.org/web/gdal-2.4.0/html/index.html here].
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* The software installs without man pages and typing gdal utilities from the command line with -help gives only a brief list of options. But the following works:
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** Download the appropriate version of sources  as tar.gz file and expand the file
 +
** install doxygen if needed, and type doxygen in the top directory of the source
 +
** Open html/index.html in a web browser
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* Documentation was installed as described above for [http://demo.openwfm.org/web/gdal-2.4.0/html/index.html version 2.4.0] and [http://demo.openwfm.org/web/gdal-3.0.0/html/index.html version 3.0.0]
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* There is https://live.osgeo.org/en/quickstart/gdal_quickstart.html
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==How to==
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===Subset a dataset===
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<pre>
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gdal_translate -projwin_srs '+proj=longlat +datum=WGS84 +no_defs' -projwin -120 39 -119 38 file.tif subset.tif
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gdal_translate -projwin_srs '+proj=stere +lat_0=38.5 +lon_0=-119.5 +datum=WGS84 +units=km +no_defs' -projwin -50 50 50 -50 file.tif subset.tif
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</pre>
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==External links==
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* https://gis.stackexchange.com/questions/164853/reading-modifying-and-writing-a-geotiff-with-gdal-in-python
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* https://spatialreference.org/ translation of EPSG codes and proj4 etc.
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* https://medium.com/planet-stories/a-gentle-introduction-to-gdal-part-1-a3253eb96082
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* https://gis.stackexchange.com/questions/33330/how-do-i-extract-a-rasters-extent-in-python
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* [https://gis.stackexchange.com/questions/175293/difference-between-datum-and-ellipsoid-for-geodetic-coordinates Datum and ellipsoid are not the same thing]
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* [https://gis.stackexchange.com/questions/42584/how-to-call-gdal-translate-from-python-code How to call gdal translate from python code]
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* [https://automating-gis-processes.github.io/2016/Lesson7-read-raster.html Reading raster files with GDAL]
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* [http://erouault.blogspot.com/2015/10/gdal-and-ogr-utilities-as-library.html GDAL and OGR utilities as library]
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* [https://stackoverflow.com/questions/2922532/obtain-latitude-and-longitude-from-a-geotiff-file Obtain latitude and longitude from a GeoTIFF file]
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* [https://pcjericks.github.io/py-gdalogr-cookbook/ Python GDAL/OGR Cookbook]
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* https://stackoverflow.com/questions/50191648/gis-geotiff-gdal-python-how-to-get-coordinates-from-pixel
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* [https://wiki.osgeo.org/wiki/OSGeo_Python_Library OSGeo Python Library]
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* [https://trac.osgeo.org/gdal/wiki/GdalOgrInPython GDAL/OGR in Python (old wiki)]
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* https://stackoverflow.com/questions/52777153/convert-longitude-latitude-to-pixel-values-using-gdal
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* https://www.geos.ed.ac.uk/~smudd/TopoTutorials/html/tutorial_raster_conversion.html
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* https://pypi.org/project/geoio/
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* https://gisgeography.com/free-gis-software/
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* https://qgis.org
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* https://www.qgistutorials.com
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* [http://www.pkrc.net/wrf-lambert.html The pitfalls of Lambert conformal projection in WRF and MM5]
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* [https://fabienmaussion.info/2018/01/06/wrf-projection Map projections in WRF: it's easy to get it wrong] includes also examples of maps from WRF using [https://pypi.org/project/salem/ salem]
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* [https://gisgeography.com/wgs84-world-geodetic-system/ WGS84] [https://gisgeography.com/nad83-north-american-datum/ NAD83] simple explanations, not technical
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* https://www.codeguru.com/cpp/g-m/bitmap/viewers/article.php/c9187/2D--3D-Visualization-Techniques-for-GeoReferenced-Images.htm
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* http://pyproj4.github.io/pyproj/html/api/geod.html
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* https://janakiev.com/blog/gps-points-distance-python/
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* https://trac.osgeo.org/gdal/ticket/4267 on stereo projection
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==Glossary==
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* WKT: [[wikipedia:Well-known text representation of coordinate reference systems|Well-known text representation of coordinate reference systems]] or [[wikipedia:Well-known_text_representation_of_geometry|Well-known text representation of geometry]], a text markup language for representing vector geometry objects
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* SRS: [[wikipedia:Spatial reference system|Spatial reference system]]: a complete set of parameters that determine how to associate a point on a map with a point on the Earth surface (system of coordinates, map projection, and datum).  
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* [[wikipedia:Latitude|Latitude]] - there is more than one because the Earth is not a sphere
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==See also==
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* [[How to run WRF-Fire with real data]]
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* [[WPS with GeoTIFF support]]

Latest revision as of 22:27, 11 June 2019

Installation

Best install using standard system package manager, such as apt-get (Ubuntu), yum (Fedora), or macports (OSX).

Download

The current download page is http://download.osgeo.org/gdal/. However, web searches for the code or documentation lead to many dead links to defuncts sites. In particular, almost all links leading inside https://gdal.org/ from internet search engines are dead.

Documentation

How to

Subset a dataset

gdal_translate -projwin_srs '+proj=longlat +datum=WGS84 +no_defs' -projwin -120 39 -119 38 file.tif subset.tif
gdal_translate -projwin_srs '+proj=stere +lat_0=38.5 +lon_0=-119.5 +datum=WGS84 +units=km +no_defs' -projwin -50 50 50 -50 file.tif subset.tif

External links

Glossary

See also