Re: [Qgis-user] r.patch fails “Input raster map contains cells with NULL-value (no-data)” (QGIS 2.18)

[Terry Morse]

Thank you for the suggestion, Richard. The VRT plugged most, but not all, the blank areas that were 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.

Terry

-----Original Message-----
From: Richard McDonnell
Sent: Feb 23, 2018 12:58 AM
To: Terry Morse
Subject: Re: [Qgis-user] r.patch fails “Input raster map contains cells with NULL-value (no-data)” (QGIS 2.18)

Hi Terry,
Try using GDAL in QGIS instead. Create a VRT (Build Virtual in processing search Bar) of the two rasters first, and then use gdal_translate (Translate in processing search Bar) to convert it to a raster format of your choice.
Hope this helps

Regards,

Richard

On 23/02/2018 00:11, Terry Morse wrote:

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:

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.

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?

Thank you,
Terry

_______________________________________________
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

--
Richard McDonnell
GIS Specialist PgD GIS AssocSCSI
OPW FRM Data Management
52 Stephens Green, Dublin 2.
TEL: 01 6476543

Email Disclaimer: http://www.opw.ie/en/disclaimer/

_______________________________________________
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user