[gdal-dev] Blue artifact dots in shadows when using GDAL to create mosaics

Chastain, Raymond Lee (MU-Student) rlc5m8 at mail.missouri.edu
Tue Oct 5 13:52:18 PDT 2021


Hi Brad,

We edited the VRT to remove the NODATA tags, we also tried "gdal_edit.py -unsetnodata", however we are still seeing the colored dot artifacts.

Could you please elaborate on what exactly you did that helped and if the dots were completely removed by that process?

Thanks again,
Raymond.
________________________________
From: gdal-dev <gdal-dev-bounces at lists.osgeo.org> on behalf of Chastain, Raymond Lee (MU-Student) <rlc5m8 at mail.missouri.edu>
Sent: Tuesday, October 5, 2021 3:13 PM
To: gdal-dev at lists.osgeo.org <gdal-dev at lists.osgeo.org>; bradh at frogmouth.net <bradh at frogmouth.net>
Subject: Re: [gdal-dev] Blue artifact dots in shadows when using GDAL to create mosaics

Thanks Brad,

I didn't notice your response as my e-mail system flagged it junk email.

We'll try this and report back with our findings.

Thank you again for the help,
Raymond.
________________________________
From: Brad Hards <bradh at frogmouth.net>
Sent: Tuesday, September 28, 2021 7:21 PM
To: gdal-dev at lists.osgeo.org <gdal-dev at lists.osgeo.org>
Cc: Chastain, Raymond Lee (MU-Student) <rlc5m8 at mail.missouri.edu>
Subject: Re: [gdal-dev] Blue artifact dots in shadows when using GDAL to create mosaics

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On Wednesday, 29 September 2021 9:37:57 AM AEST Chastain, Raymond Lee (MU-
Student) wrote:
> Process is very simple
>
>   1.  Take our tiles and build a virtual raster:
> gdalbuildvrt -r lanczos -resolution HIGHEST output.vrt -input_file_list
> input_file_list.txt 2.  Convert our virtual raster to a GeoTIFF:
>   3.  gdal_translate -of GTIFF ./output.vrt ./output.tif
I manually removed the NODATA part from the vrt, and it looks better. Possibly
the nodata value in the source is bad? Or you need to put something more
meaningful behind the images...

Brad




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