1gdaladdo(1)                 General Commands Manual                gdaladdo(1)
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NAME

6       gdaladdo - gdaladdo builds or rebuilds overview images
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SYNOPSIS

9       gdaladdo [-r {nearest,average,average_mp,average_magphase,mode}]
10                       filename levels
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DESCRIPTION

13       The gdaladdo utility can be used to build or rebuild overview images
14       for most supported file formats with one over several downsampling
15       algorithms.
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17       -r {nearest,average,average_mp,average_magphase,mode}:
18           Select a resampling algorithm.
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20       filename:
21           The file to build overviews for.
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23       levels:
24           A list of integral overview levels to build.
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26       Mode is not actually implemented, and average_mp is unsuitable for use.
27       Average_magphase averages complex data in mag/phase space. Nearest and
28       average are applicable to normal image data. Nearest applies a nearest
29       neighbour (simple sampling) resampler, while average computes the
30       average of all non-NODATA contributing pixels.
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32       Selecting a level value like 2 causes an overview level that is 1/2 the
33       resolution (in each dimension) of the base layer to be computed. If the
34       file has existing overview levels at a level selected, those levels
35       will be recomputed and rewritten in place.
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37       Some format drivers do not support overviews at all. Many format
38       drivers store overviews in a secondary file with the extension .ovr
39       that is actually in TIFF format. The GeoTIFF driver stores overviews
40       internally to the file operated on.
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42       Overviews created in TIFF format may be compressed using the
43       COMPRESS_OVERVIEW configuration option. All compression methods,
44       supported by the GeoTIFF driver, available here. (eg --config
45       COMPRESS_OVERVIEW DEFLATE)
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47       Most drivers also support an alternate overview format using Erdas
48       Imagine format. To trigger this use the USE_RRD=YES configuration
49       option. This will place the overviews in an associated .aux file
50       suitable for direct use with Imagine or ArcGIS as well as GDAL
51       applications. (eg --config USE_RRD YES)
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EXAMPLE

54       Create overviews, embedded in the supplied TIFF file:
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56       gdaladdo -r average abc.tif 2 4 8 16
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58       Create an external compressed GeoTIFF overview file from the ERDAS .IMG
59       file:
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61       gdaladdo --config COMPRESS_OVERVIEW DEFLATE erdas.img 2 4 8 16
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63       Create an Erdas Imagine format overviews for the indicated JPEG file:
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65       gdaladdo --config USE_RRD YES airphoto.jpg 3 9 27 81
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AUTHORS

68       Frank Warmerdam <warmerdam@pobox.com>, Silke Reimer
69       <silke@intevation.de>
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73GDAL                              31 Jul 2007                      gdaladdo(1)
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