gdal-cheat-sheet.rst

GDAL Cheat Sheet

本文为 GitHub 上的项目，原项目地址： https://github.com/dwtkns/gdal-cheat-sheet

Vector operations

Get vector information

ogrinfo -so input.shp layer-name

Or, for all layers

ogrinfo -al -so input.shp

Print vector extent

ogrinfo input.shp layer-name | grep Extent

List vector drivers

ogr2ogr --formats

Convert between vector formats

ogr2ogr -f "GeoJSON" output.json input.shp

Clip vectors by bounding box

ogr2ogr -f "ESRI Shapefile" output.shp input.shp -clipsrc
        <x_min> <y_min> <x_max> <y_max>

Clip one vector by another

ogr2ogr -clipsrc clipping_polygon.shp output.shp input.shp

Reproject vector:

ogr2ogr output.shp -t_srs "EPSG:4326" input.shp

Merge features in a vector file by attribute ("dissolve")

ogr2ogr -f "ESRI Shapefile" dissolved.shp input.shp -dialect sqlite -sql
  "select ST_union(Geometry),common_attribute from input GROUP BY common_attribute"

Merge vector files:

ogr2ogr merged.shp input1.shp
ogr2ogr -update -append merged.shp input2.shp -nln merged

Extract from a vector file based on query

To extract features with STATENAME 'New York','New Hampshire', etc. from states.shp

ogr2ogr -where 'STATENAME like "New%"' states_subset.shp states.shp

To extract type 'pond' from water.shp

ogr2ogr -where "type = pond" ponds.shp water.shp

Subset & filter all shapefiles in a directory

Assumes that filename and name of layer of interest are the same...

ls -1 *.shp | sed 's/.shp//g' | xargs -n1 -I % ogr2ogr %-subset.shp %.shp
   -sql "SELECT field-one, field-two FROM '%' WHERE field-one='value-of-interest'"

Raster operations

Get raster information

gdalinfo input.tif

List raster drivers

gdal_translate --formats

Convert between raster formats

gdal_translate -of "GTiff" input.grd output.tif

Convert 16-bit bands (Int16 or UInt16) to Byte type (Useful for Landsat 8 imagery...)

gdal_translate -of "GTiff" -co "COMPRESS=LZW" -scale 0 65535 0 255
    -ot Byte input_uint16.tif output_byte.tif

You can change '0' and '65535' to your image's actual min/max values to preserve more color variation or to apply the scaling to other band types - find that number with:

gdalinfo -mm input.tif | grep Min/Max

Convert a directory of files to a different raster format

ls -1 *.img | sed 's/.img//g' | xargs -n1 -I % gdal_translate
        -of "GTiff" %.img %.tif

Reproject raster:

gdalwarp -t_srs "EPSG:102003" input.tif output.tif

Be sure to add -r bilinear if reprojecting elevation data to prevent funky banding artifacts.

Georeference an unprojected image with known bounding coordinates:

gdal_translate -of GTiff -a_ullr <top_left_lon> <top_left_lat>
    <bottom_right_lon> <bottom_right_lat> -a_srs EPSG:4269 input.png output.tif

Clip raster by bounding box

gdalwarp -te <x_min> <y_min> <x_max> <y_max> input.tif clipped_output.tif

Clip raster to SHP / NoData for pixels beyond polygon boundary

gdalwarp -dstnodata <nodata_value> -cutline input_polygon.shp
    input.tif clipped_output.tif

Crop raster dimensions to vector bounding box

gdalwarp -cutline cropper.shp -crop_to_cutline input.tif cropped_output.tif

Merge rasters

gdal_merge.py -o merged.tif input1.tif input2.tif

Alternatively,

gdalwarp input1.tif input2.tif merged.tif

Or, to preserve nodata values:

gdalwarp input1.tif input2.tif merged.tif -srcnodata <nodata_value>
    -dstnodata <merged_nodata_value>

Stack grayscale bands into a georeferenced RGB

Where LC81690372014137LGN00 is a Landsat 8 ID and B4, B3 and B2 correspond to R,G,B bands respectively:

gdal_merge.py -co "PHOTOMETRIC=RGB" -separate LC81690372014137LGN00_B{4,3,2}.tif
    -o LC81690372014137LGN00_rgb.tif

Fix an RGB TIF whose bands don't know they're RGB

gdal_merge.py -co "PHOTOMETRIC=RGB" input.tif -o output_rgb.tif

Export a raster for Google Earth

gdal_translate -of KMLSUPEROVERLAY input.tif output.kmz -co FORMAT=JPEG

Raster calculation (map algebra)

Average two rasters:

gdal_calc.py -A input1.tif -B input2.tif --outfile=output.tif --calc="(A+B)/2"

Add two rasters:

gdal_calc.py -A input1.tif -B input2.tif --outfile=output.tif --calc="A+B"

etc.

Create a hillshade from a DEM

gdaldem hillshade -of PNG input.tif hillshade.png

Change light direction:

gdaldem hillshade -of PNG -az 135 input.tif hillshade_az135.png

Use correct vertical scaling in meters if input is projected in degrees

gdaldem hillshade -s 111120 -of PNG input_WGS1984.tif hillshade.png

Apply color ramp to a DEM First, create a color-ramp.txt file: (Height, Red, Green, Blue)

0 110 220 110
900 240 250 160
1300 230 220 170
1900 220 220 220
2500 250 250 250

Then apply those colors to a DEM:

gdaldem color-relief input.tif color_ramp.txt color-relief.tif

Create slope-shading from a DEM First, make a slope raster from DEM:

gdaldem slope input.tif slope.tif

Second, create a color-slope.txt file: (Slope angle, Red, Green, Blue)

0 255 255 255
90 0 0 0

Finally, color the slope raster based on angles in color-slope.txt:

gdaldem color-relief slope.tif color-slope.txt slopeshade.tif

Resample (resize) raster

gdalwarp -ts <width> <height> -r cubicspline dem.tif resampled_dem.tif

Entering 0 for either width or height guesses based on current dimensions.

Burn vector into raster

gdal_rasterize -b 1 -i -burn -32678 -l layername input.shp input.tif

Create contours from DEM

gdal_contour -a elev -i 50 input_dem.tif output_contours.shp

Get values for a specific location in a raster

gdallocationinfo -xml -wgs84 input.tif <lon> <lat>

Other

Convert KML points to CSV (simple)

ogr2ogr -f CSV output.csv input.kmz -lco GEOMETRY=AS_XY

Convert KML to CSV (WKT) First list layers in the KML file

ogrinfo -so input.kml

Convert the desired KML layer to CSV

ogr2ogr -f CSV output.csv input.kml -sql "select *,OGR_GEOM_WKT from some_kml_layer"

CSV points to SHP This section needs retooling Given input.csv

lon_column,lat_column,value
-81,32,13
-81,32,14
-81,32,15

Make a .dbf table for ogr2ogr to work with from input.csv

ogr2ogr -f "ESRI Shapefile" input.dbf input.csv

Use a text editor to create a .vrt file in the same directory as input.csv and input.dbf. This file holds the parameters for building a full shapefile based on values in the DBF you just made.

<OGRVRTDataSource>
  <OGRVRTLayer name="output_file_name">
    <SrcDataSource relativeToVRT="1">./</SrcDataSource>
    <SrcLayer>input</SrcLayer>
    <GeometryType>wkbPoint</GeometryType>
    <LayerSRS>WGS84</LayerSRS>
    <GeometryField encoding="PointFromColumns" x="lon_column" y="lat_column"/>
  </OGRVRTLayer>
</OGRVRTDataSource>

Create shapefile based on parameters listed in the .vrt

mkdir shp
ogr2ogr -f "ESRI Shapefile" shp/ inputfile.vrt

The VRT file can be modified to give a new output shapefile name, reference a different coordinate system (LayerSRS), or pull coordinates from different columns.

MODIS operations

First, download relevant .hdf tiles from the MODIS ftp site: ftp://ladsftp.nascom.nasa.gov/; use the MODIS sinusoidal grid for reference.

Create a file containing the names of all .hdf files in the directory

ls -1 *.hdf > files.txt

List MODIS Subdatasets in a given HDF (conf. the MODIS products table)

gdalinfo longFileName.hdf | grep SUBDATASET

Make TIFs from each file in list; replace 'MOD12Q1:Land_Cover_Type_1' with desired Subdataset name

mkdir output
cat files.txt | xargs -I % -n1 gdalwarp -of GTiff
    'HDF4_EOS:EOS_GRID:%:MOD12Q1:Land_Cover_Type_1' output/%.tif

Merge all .tifs in output directory into single file

cd output
gdal_merge.py -o Merged_Landcover.tif *.tif

BASH functions

Size Functions

This size function echos the pixel dimensions of a given file in the format expected by gdalwarp.

function gdal_size() {
    SIZE=$(gdalinfo $1 |\
        grep 'Size is ' |\
        cut -d\   -f3-4 |\
        sed 's/,//g')
    echo -n "$SIZE"
}

This can be used to easily resample one raster to the dimensions of another:

gdalwarp -ts $(gdal_size bigraster.tif) -r cubicspline
    smallraster.tif resampled_smallraster.tif

Extent Functions

These extent functions echo the extent of the given file in the order/format expected by gdal_translate -projwin. (Originally from Linfiniti).

function gdal_extent() {
    if [ -z "$1" ]; then
        echo "Missing arguments. Syntax:"
        echo "  gdal_extent <input_raster>"
        return
    fi
    EXTENT=$(gdalinfo $1 |\
        grep "Upper Left\|Lower Right" |\
        sed "s/Upper Left  //g;s/Lower Right //g;s/).*//g" |\
        tr "\n" " " |\
        sed 's/ *$//g' |\
        tr -d "[(,]")
    echo -n "$EXTENT"
}

function ogr_extent() {
    if [ -z "$1" ]; then
        echo "Missing arguments. Syntax:"
        echo "  ogr_extent <input_vector>"
        return
    fi
    EXTENT=$(ogrinfo -al -so $1 |\
        grep Extent |\
        sed 's/Extent: //g' |\
        sed 's/(//g' |\
        sed 's/)//g' |\
        sed 's/ - /, /g')
    EXTENT=`echo $EXTENT | awk -F ',' '{print $1 " " $4 " " $3 " " $2}'`
    echo -n "$EXTENT"
}

function ogr_layer_extent() {
    if [ -z "$2" ]; then
        echo "Missing arguments. Syntax:"
        echo "  ogr_extent <input_vector> <layer_name>"
        return
    fi
    EXTENT=$(ogrinfo -so $1 $2 |\
        grep Extent |\
        sed 's/Extent: //g' |\
        sed 's/(//g' |\
        sed 's/)//g' |\
        sed 's/ - /, /g')
    EXTENT=`echo $EXTENT | awk -F ',' '{print $1 " " $4 " " $3 " " $2}'`
    echo -n "$EXTENT"
}

Extents can be passed directly into a gdal_translate command like so:

gdal_translate -projwin $(ogr_extent boundingbox.shp) input.tif clipped_output.tif

or

gdal_translate -projwin $(gdal_extent target_crop.tif) input.tif clipped_output.tif

This can be a useful way to quickly crop one raster to the same extent as another. Add these to your ~/.bash_profile file for easy terminal access.

Sources

http://live.osgeo.org/en/quickstart/gdal_quickstart.html

https://github.com/nvkelso/geo-how-to/wiki/OGR-to-reproject,-modify-Shapefiles

ftp://ftp.remotesensing.org/gdal/presentations/OpenSource_Weds_Andre_CUGOS.pdf

http://developmentseed.org/blog/2009/jul/30/using-open-source-tools-make-elevation-maps-afghanistan-and-pakistan/

http://linfiniti.com/2010/12/a-workflow-for-creating-beautiful-relief-shaded-dems-using-gdal/

http://linfiniti.com/2009/09/clipping-rasters-with-gdal-using-polygons/

http://nautilus.baruch.sc.edu/twiki_dmcc/bin/view/Main/OGR_example

http://www.gdal.org/frmt_hdf4.html

http://planetflux.adamwilson.us/2010/06/modis-processing-with-r-gdal-and-nco.html

http://trac.osgeo.org/gdal/wiki/FAQRaster

http://www.mikejcorey.com/wordpress/2011/02/05/tutorial-create-beautiful-hillshade-maps-from-digital-elevation-models-with-gdal-and-mapnik/

http://dirkraffel.com/2011/07/05/best-way-to-merge-color-relief-with-shaded-relief-map/

http://gfoss.blogspot.com/2008/06/gdal-raster-data-tips-and-tricks.html

http://osgeo-org.1560.x6.nabble.com/gdal-dev-Dissolve-shapefile-using-GDAL-OGR-td5036930.html

https://www.mapbox.com/tilemill/docs/guides/terrain-data/

https://gist.github.com/ashaw/0862ec044c45b9aa3c76

https://github.com/gina-alaska/dans-gdal-scripts