[FWTools] gdal_merge with a specific pixel value clipped/removed

[Matt.Wilkie at gov.yk.ca]

The error is because you need to quote the argument values to keep them from being interpreted as filenames:

	gdal_merge -n “230 245 255” ...

However gdal_merge can't use different nodata values for each band. You need to pre-process the files before merging. This worked for me here:

Create  VRT (virtual raster) file for the input file(s):

	gdalbuildvrt -srcnodata "230 245 255”"  infile1.vrt  infile1.tif

Then feed the .vrt's to gdal_merge:

	gdal_merge -of merged_result.tif infile1.vrt infile2.vrt ...


You may need to switch from fwtools to Osgeo4w (if on Windows) to get gdalbuildvrt.

Cheers,

-- 
matt wilkie
--------------------------------------------
Geomatics Analyst
Information Management and Technology
Yukon Department of Environment
10 Burns Road * Whitehorse, Yukon * Y1A 4Y9
867-667-8133 Tel * 867-393-7003 Fax
http://environmentyukon.gov.yk.ca/geomatics/
--------------------------------------------



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From: fwtools-bounces at lists.maptools.org [mailto:fwtools-bounces at lists.maptools.org] On Behalf Of Ari Simmons
Sent: Tuesday, June 09, 2015 12:43 PM
To: fwtools at lists.maptools.org
Subject: [FWTools] gdal_merge with a specific pixel value clipped/removed

I have a large set of .tif files and I need to merge/mosaic them all into one .tif with the no-data value removed (i.e. value 230, 245, 255). However, when I put this in...pixel '230, 245, 255' becomes '0, 245, 255').
I am trying to get NO PIXEL returned for 230, 245, 255. Is that possible?
I:\TFS_6\trial_merge>gdal_merge.py -o test.tif -n 230 245 255 file1.tif file2.tif

ERROR 4: `245' does not exist in the file system,
and is not recognised as a supported dataset name.

ERROR 4: `255' does not exist in the file system,
and is not recognised as a supported dataset name.

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