I have two geotiff images that I would like to resample the same resolution. If I use ArcGIS this would be easy to do. But using QGIS I don't know how to do this. Some help will be very appreciate. Thanks.
This is easy in QGIS too, though a little less obvious. There are a couple of ways you can do it:
- Raster Calculator - simply use the raster calculator and you can set the resolution and extent there and can make them match another raster by selecting the raster band you want to match in the Raster Bands list and then clicking the "Current layer extent" button. The columns and rows fields will let you set the resolution. However, this method gives you no control over the resampling method.
- Using GDAL_Warp - this tool lets you set the output resolution either by specifying the width and height of the output raster or by specifying the -tr switch (see the documentation). You can get to the GDAL_warp tool by going Raster->Projections->Warp (I did say it wasn't obvious from a resampling point of view!). If you want to use the -tr switch, fill in all the boxes for input raster and output etc (your source and target SRS values will presumably be the same in this case - though don't have to be if you're reprojecting as well). Then click the little pencil icon at the bottom and edit the auto-generated gdal-warp commandline to include your -tr switch. Gdal_wrap lets you specif the algorithm you want to use for the resampling and so is a little less of a blunt instrument than using the raster calculator.
I normally use the Raster Alignment tool.
It's localized in the raster tab and can be used to set rasters to the same extent too. It can also perform some operations when resampling to a new resolution (such as mean, min and max value, etc.).
Here is a link with some info on it: https://docs.qgis.org/2.18/en/docs/user_manual/working_with_raster/raster_analysis.html?highlight=raster%20alignment#id3
I use the 2.18.13 version. I don't know if the tool is available in older versions.