I am currently using GRASS GIS 7.4.1. I need some help here:

when loading a geotiff made in QGIS to GRASS GIS, the bands that make the image are split (e.g.clip1@permanent, clip2@permanent, & so on..)and I have to load them individually to the GRASS GIS canvas and then make a composite. Why is this so?

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    Please Edit your question so that the title is not in ALL CAPS (using only uppercase attracts downvotes and reduces the number of people willing to read the question) and choose a single question to ask for this Question (as per the Tour). – Vince Oct 26 '18 at 20:25
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    The first two parts of the OP's question are related and can be addressed in a single answer. The third part, running supervised classification, deserves a separate post. So I'd suggest that the OP rewrite his question first including only the sections on importing rasters for classification.BTW, GRASS GIS is typically written as all caps, since it's an abbreviation. – Micha Oct 28 '18 at 14:36

GRASS GIS like other GIS imaging processing software splits a multiband raster into individual bands on import. This is to allow preparing various analysis results from individual band combinations, such as false color images or NDVI from satellite data. For example Landsat 8 contains 11 bands. Bands 5 and 4 can be used to calculate NDVI. Bands 5,3,2 are sometimes used to produce false color images.

If you need to recombine the imported bands for visualization, the r.composite module does this. You can create a true color composite by passing the r, g, and b parameters the bands that should appear as red, green and blue. i.e. (the Landsat 8 example)

r.composite r=band.4  g=band.3 b=band.2 out=l8_rgb_composite

Here is a video tutorial in performing a supervised classification in GRASS GIS 7.6.1. It also contains some importing basics. Table of Contents to help jump.


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