Multispectral imagery collected by satellite payloads containing imaging sensors are widely used for geospatial studies.
A popular source of such satellite imagery is NASA’s Landsat constellation of satellites. Landsat satellites have been collecting imagery for over 40 years. There is a wealth of imagery available. One of the primary objectives of Landsat was to provide imagery for agriculture, geology, forestry, regional planning, education, mapping, and global change research. Landsat images have also been used for emergency response and disaster relief.
Multispectral imagery differs from standard colour aerial or satellite imagery as it captures images using different portions of the electromagnetic spectrum. This allows analysis of the land, ocean and atmosphere by depicting electromagnetic radiation that is not visible to the human eye. The human eye is only able to visualise wavelengths roughly between 400nm to 700nm, this makes up what we call the visible spectrum. This means we cannot see Near Infrared, Infrared or Far infrared electromagnetic radiation, along with the rest of the EM spectrum such as x-rays, extreme ultraviolet or at the other end of the spectrum radio waves. Interestingly other animals and insects can see different portions of the EM spectrum, allowing them to see ultraviolet light for example, this allows them to identify such things as pollen on flowers.
In order to use this imagery in MapInfo Pro Advanced, it can first be downloaded free of charge from https://landsat.usgs.gov/landsat-data-access. Choose the bands that are required for the type of study to be undertaken. Information can be found here https://landsat.usgs.gov/what-are-best-spectral-bands-use-my-study.
Once the data is downloaded, it will be provided in tiles. The tiles will contain the data as separate bands or images. The files can be opened via File > Open in MapInfo Pro Advanced. Select Raster Image under the File of Type drop down.
There will be a separate TIF image for the same area that has been captured in a different bandwidth.
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As these are opened in to MapInfo Pro Advanced, they will likely display as greyscale images. In order to manipulate and change the band combinations, the multiple images need to be combined together in to a single image. This is one of the benefits of the MRR capability in MapInfo Pro Advanced. Combining is different to Merging. Combining adds the multiple images for the same geographic area into a single file with multiple bands. Merging is more often used to stitch together multiple images that do not overlap but are side by side in order to increase the area of coverage of a single image.
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In order to Merge the images together, go to Raster > Raster Operations > Merge. Select all of the images from the directory of choice. Note the files do not need to be opened in the MapInfo window. Use the file open tool in the Merge callout window. This will save on system resources. Choose an output file name to save too. Click Process.
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Once the process has finished, open the new file in a map window. Return to the Raster tab. Click on Bands. You will see a list of options for changing bands combinations. This can be done manually, alternatively use some of the existing known templates for Landsat 7 and Landsat 8.
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In order to toggle through the different combinations, hover the cursor over the template and wait for the change, you can preview before finalising with a click.
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Areas of interest can be digitised in to vector layers or the classification and contour tools could be applied in order to highlight specific areas of land.