The Landsat/Sentinel images are composed of different bands, each represented by a different portion of the electromagnetic spectrum, to work with the combination of Landsat bands, first it is necessary to understand the specifications of each band (according to the NASA report), such as the values for Landsat 8.
- Band 1 (Ultra Blue coastal/aerosol 0.435 – 0.451 µm, resolution: 30 m).- senses deep blues and violets. Blue light is hard to collect from space because it’s scattered easily by tiny bits of dust and water in the air, and even by air molecules themselves. This is one reason why very distant things (like mountains on the horizon) appear blueish, and why the sky is blue.
- Band 2 (Blue 0.452 – 0.512 µm, resolution: 30 m).- is very useful for mapping water bodies, differentiation between soil and vegetation, differentiation between coniferous and decisive vegetation, its disadvantage is susceptibility to atmospheric dispersion, it is the “noisiest” band.
- Band 3 (Green 0.533 – 0.590 µm, resolution: 30 m).- designed to evaluate the vigor of healthy vegetation, differentiate rock types and measure water quality.
- Band 4 (Red 0.636 – 0.673 µm, resolution: 30 m).- allows to determine the absorption of chlorophyll, therefore very useful for the classification of vegetation cover, agriculture and land use.
- Band 5 (Near Infrared (NIR) 0.851 – 0.879 µm, resolution: 30 m).- measures the near infrared, or NIR. This part of the spectrum is especially important for ecology because healthy plants reflect it – the water in their leaves scatters the wavelengths back into the sky. By comparing it with other bands, we get indexes like NDVI, which let us measure plant health more precisely than if we only looked at visible greenness.
- Band 6 (Shortwave Infrared (SWIR 1) 1.566 – 1.651 µm, resolution: 30 m).- cover different slices of the shortwave infrared, or SWIR. They are particularly useful for telling wet earth from dry earth, and for geology: rocks and soils that look similar in other bands often have strong contrasts in SWIR.
- Band 7 (Shortwave Infrared (SWIR 2) 2.107 – 2.294 µm, resolution: 30 m).- has similar applications to band 6.
- Band 8 (Panchromatic 0.503 – 0.676 µm, resolution: 15 m).- is the panchromatic – or just pan – band. It works just like black and white film: instead of collecting visibile colors separately, it combines them into one channel.
- Band 9 (Cirrus 1.363 – 1.384 µm, resolution: 30 m).- shows the least, yet it’s one of the most interesting features of Landsat 8. It covers a very thin slice of wavelengths: only 1370 ± 10 nanometers. Few space-based instruments collect this part of the spectrum, because the atmosphere absorbs almost all of it. Landsat 8 turns this into an advantage.
- Band 10 (Thermal Infrared (TIRS 1) 10.60 – 11.19 µm, resolution: 100 m).- is in the thermal infrared, or TIR – see heat. Instead of measuring the temperature of the air, like weather stations do, they report on the ground itself, which is often much hotter.
- Band 11 (Thermal Infrared (TIRS 2) 11.50 – 12.51 µm, resolution: 100 m).- performs similar functions to band 10.
Once we have understood about each band we proceed to download Landsat 8 satellite images, with a compressor like 7Zip or WinRAR decompress the images.
From ArcMap upload the image bands with the Add Data button on the toolbar:
To perform spectral compositions directly, open the Composite Bands tool located at:
ArcToolbox > Data Management Tools > Raster > Raster Processing
In the Input Rasters add the bands (Landsat 8) in the order (RGB: 432) in which you want to compose them. Finally accept to conclude with the combination of satellite bands.
