For this exercise we use a Landsat-8 image of Portugal (path: 204, row: 32). Landsat satellite data is available on https://earthexplorer.usgs.gov/.
A Landsat-8 image consists of several bands, each represented with a TIFF file in your data download. Each file contains radiance data of the Earth surface within a certain window of the spectrum.
| band | wavelength (μm) | resolution (m) |
| B1 | 0.433 – 0.453 | 30 |
| B2 | 0.450 – 0.515 | 30 |
| B3 | 0.525 – 0.600 | 30 |
| B4 | 0.630 – 0.680 | 30 |
| B5 | 0.845 – 0.885 | 30 |
| B6 | 1.560 – 1.660 | 30 |
| B7 | 2.100 – 2.300 | 30 |
| B8 | 0.500 – 0.680 | 15 |
| B9 | 1.360 – 1.390 | 30 |
| B10 | 10.6 – 11.2 | 100 |
| B11 | 11.5 – 12.5 | 100 |
A Landsat TIFF file of any band can be imported as an individual or as a merged layer into QGIS.
Import an individual layer
In the toolbar:
Layer >> Add Layer >> Add Raster Layer…
Click […] to navigate to your folder and select your TIFF file of choice. Click [Add] to import your Landsat-8 image file into the map canvas. In our case, we imported the band 5 image LC08_L1TP_204032_20191230_20200111_01_T1_B5.TIFF:
Band 5 represents near-infrared or NIR. A part of the spectrum that is reflected back by healthy vegetation. For example, well-irrigated vegetation will appear bright in the image as water in the leaves scatters back the near-infrared wavelengths.
Import as a merged layer
Band combinations usually provide more information than the bands individually. In the following example we will create a natural colour image by combining band 4, 3 and 2, respectively representing visible red, green and blue.
In the toolbar:
Raster >> Miscellaneous >> Merge…
Click […]. Another window opens where we click [Add file(s)…] to navigate to your folder and select the B2, B3 and B4 bands.
Make sure that the order of your bands in the window are B4, B3 and B2 as is shown in the image below:
QGIS allows you to drag and drop the files in the right order. Click [Ok] to return to the first window.
Check [] Place each input file into a separate band. By doing so, you create a composite image.
Save your output file by clicking […] after Merged >> Save to File… Navigate to your folder of choice and give a name accordingly.
In our example your window for merging should look like this:
Click [Run] to import the natural colour image to the map canvas.
The colours of the composite image come close to what we see with our own eyes. Only, a natural colour image can often look somewhat hazy. This is due to the scattering of blue light by the atmosphere.
Image courtesy of the U.S. Geological Survey
Landsat-8, sensor: OLI_TIRS, path 204, row 32, date acquired: 2019-12-30
Landsat product ID: LC08_L1TP_204032_20191230_20200111_01_T1