<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-size: 13px;color: rgb(0, 0, 0);font-family: arial, sans-serif;">Thank you for the suggestion, Richard. The VRT plugged most, but not all, the blank areas that <i>were </i>covered by the two independent raster layers. I'm not sure why it didn't, so I'm left with using the two layers. Still, I learned a new raster skill, so it was worth trying. I'll have to try to figure out r.patch in GRASS. Another useful learning experience.<br><br>Terry<br><blockquote style="padding-left: 5px; margin-left: 0px; border-left: #0000ff 2px solid; font-weight: normal; font-style: normal; text-decoration: none; font-size: 10pt; font-family: arial,sans-serif; color: black;">-----Original Message-----
<br>From: Richard McDonnell <richard.mcdonnell@opw.ie>
<br>Sent: Feb 23, 2018 12:58 AM
<br>To: Terry Morse <tmorse@teleport.com>
<br>Subject: Re: [Qgis-user] r.patch fails “Input raster map contains cells with NULL-value (no-data)” (QGIS 2.18)
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Hi Terry,<br>
Try using GDAL in QGIS instead. Create a VRT (<b>Build Virtual</b>
in processing search Bar) of the two rasters first, and then use
gdal_translate (<b>Translate</b> in processing search Bar) to
convert it to a raster format of your choice.<br>
Hope this helps<br>
<br>
Regards,<br>
<br>
Richard<br>
<br>
<div class="moz-cite-prefix">On 23/02/2018 00:11, Terry Morse wrote:<br>
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<blockquote cite="mid:594222780.15279.1519344660781@wamui-megara.atl.sa.earthlink.net" type="cite">
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<div style="font-size: 13px;color: rgb(0, 0, 0);font-family:
arial, sans-serif;"><font size="2">In QGIS 2.18.16 with GRASS
7.4.0 (Windows 7, 64 bit), I am trying to create a composite
raster layer from two nearly identical versions of a 3-band
color geotiff that almost (but not quite perfectly) overlap,
using the GRASS tool r.patch. Whether or not I select the "use
zero for transparency instead of null," the process fails with
the error message:<br>
<br>
<i>Input raster map contains cells with NULL-value (no-data).
The value 255 will be used to represent no-data values in
the input map. You can specify a nodata value with the
nodata option. WARNING: The default nodata value is present
in rasterband and would lead to data loss. Please specify a
custom nodata value with the nodata parameter. ERROR: Raster
export aborted.<br>
</i><br>
Can anyone help me out with how to make this work within QGIS?
There doesn't appear to be any way to set the nodata parameter
within the r.patch dialogue box. Also, what value should I set
it to?<br>
<br>
Thank you,<br>
Terry</font><br>
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<div class="moz-signature">-- <br>
<b><u>Richard McDonnell</u></b><br>
<b><small><small><small>GIS Specialist PgD GIS AssocSCSI</small></small></small></b><br>
<b><small>OPW FRM Data Management</small></b><br>
<b><small>52 Stephens Green, Dublin 2.</small></b><br>
<small><small>TEL: 01 6476543</small></small></div>
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