gdal_merge repeats images in different locations

[matt.wilkie@…]

this can only be really described with an image, but from the output raster what
it looks like is happening is that at least some of the input files are merged
in several times but each time in a different spatial location.

In the attached screen shot, the green squares were created with "gdaltindex
250k_index $srcdir/*.tif", the blue lines are canadian province & territory
outlines, and the background raster is a geotiff dem made with:

$ gdal_merge.py -n -9999 -init -9999 -o canada_250k_dem.tif $srdirc/*.tif

Thinking I might be seeing an artifact of OpenEV just not being able to open a
10gb image from the network I downsampled the image to 1% of original size using
gdal_translate but it still looks the same.

The source rasters are some 94 tif images ranging in size from 24mb to 88mb.

[matt.wilkie@…]

screenshot showing repeated images, and index overlay

[matt.wilkie@…]

based on information from Frank Warmerdam in an email I'm trying to re-create
the mosiack using gdal_merge -creatonly and then gdalwarp to do the actual
mosaicking. However after four days it has only processed 17 of the 94 input
images, so I don't know yet whether it will work. The gdal_merge mosiack took
less than 24 hours.

[maphew]

I gave up trying to reproduce the problem with gdalwarp. A much greater than 4 times increase in time spent is just too many days to lose my computer to.

[warmerdam]

OK, I guess it should be closed then.