[Qgis-user] merging parts from various raster files

Tue Apr 30 06:45:31 PDT 2024

Hi Sibylle,
To extract the Bioregions, I suggest you utilise the option Selected features only which is a tick box below, where you select Mask layer. All you need to do is select, on the map canvas, the bioregion you want to extract.

QGIS is capable of loading Tiff's I use them exclusively in any Raster work I do. The virtual raster<https://gdal.org/drivers/raster/vrt.html> is just an easy way for you to merge/mosaic the raster's (10-12 Raster's) together into a single raster.
Kind Regards,

Richard

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From: QGIS-User <qgis-user-bounces at lists.osgeo.org> On Behalf Of Sibylle Stöckli via QGIS-User
Sent: 30 April 2024 14:10
To: 'Frank Broniewski' <broniewski at a-a.lu>; qgis-user at lists.osgeo.org; broniewski at a-a.lu
Subject: Re: [Qgis-user] merging parts from various raster files

Hello Frank and Richard
,
I have 10-12 raster files (figure 1, .tif files), they all look the same and cover the entire country with no definition of the biogeregions.
Second there is the shape file defining the biogeoregions (figure 2, different colors).

-          Probably I first need to extract the different biogeoregions out from each raster file or define the linkage between the raster files the the biogeoregions in the shape file. However, raster - crop raster based on layer mask extracts the entire mask (entire country) not the different biogeoregions.
-          Furter I may delete all the data in the raster files not needed: e.g. in raster 1  just data on biogeo 1, but not the other biogeoregions, in raster 2, data on biogeo 2, but not the other biogeregions. By doing so there will be no overlap, as each raster file consists only one biogregions.
-          I am not sure about the virtual raster, because it is not possible to import .tif files.
-          Then I may just use the "merge" function - merging each bioregions.

Background: postprocessing of a model output. It was not possible to run the model only for biogeoregion 1 (with input data from biogeoregion 1) , bioregion 2 (with input data from bioregion 2) etc. It was necessary to model the entire country with input data from bioregion 1 etc.

Kind regards
Sibylle

Figure 1
[cid:image003.jpg at 01DA9B0B.B9FA38E0]
Figure 2
[cid:image005.jpg at 01DA9B0B.B9FA38E0]
From: Frank Broniewski <broniewski at a-a.lu<mailto:broniewski at a-a.lu>>
Sent: Tuesday, April 30, 2024 1:48 PM
To: qgis-user at lists.osgeo.org<mailto:qgis-user at lists.osgeo.org>; sibylle.stoeckli at gmx.ch<mailto:sibylle.stoeckli at gmx.ch>
Subject: AW: [Qgis-user] merging parts from various raster files

Hello Sybille,

I am not sure if I understand your problem correctly. I assume, you have a mosaic of raster files (that overlap) and you want to create a single raster file for statistical analysis. In my opinion, the easiest way to achieve that is to create a virtual raster (VRT) and either use that for stats or create a new raster file from the VRT. You can find the tool in the processing toolbox. With the tool you can even define the resolution, if mixed, and how the VRT should be resampled.

HTH
Frank

https://docs.qgis.org/3.34/en/docs/user_manual/processing_algs/gdal/rastermiscellaneous.html#build-virtual-raster
________________________________
Von: QGIS-User <qgis-user-bounces at lists.osgeo.org<mailto:qgis-user-bounces at lists.osgeo.org>> im Auftrag von Sibylle Stöckli via QGIS-User <qgis-user at lists.osgeo.org<mailto:qgis-user at lists.osgeo.org>>
Gesendet: Dienstag, 30. April 2024 11:34
An: qgis-user at lists.osgeo.org<mailto:qgis-user at lists.osgeo.org> <qgis-user at lists.osgeo.org<mailto:qgis-user at lists.osgeo.org>>
Betreff: [Qgis-user] merging parts from various raster files

Dear community

I am working with QGIS 3.34 (Prizren) and would like to merge region 1 from
raster (.tif) file 1 and region 2 from raster file 2, and...
For sure I will need to use raster-miscellaneous-merge.

My question is related to the pre-processing of the input raster files.
- The 12 raster files all have the same coordinate system.
- The raster files are fully overlapping (the entire country).
- The region is not defined per se in the raster file, but in an additional
shape file (biogeo.shp).
- For sure I can carry out some zonal statistics using raster and shape
file, but to merge the regions I need all the pixels form a regions as input
file for the merging process. This process is more than just selecting
regions or cropping. Do you have any suggestions?

Kind regards
Sibylle

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