From GIS to Remote SensingI have released a new beta of the Semi-Automatic Classification Plugin v.4.0 in the official repository of QGIS (experimental).
I have added a new function that was not present in the previous beta versions: a tab Band calc for calculation of raster bands using the functions provided by NumPy.
With this new tool it is possible to perform operations between raster bands such as: sum, product, sine, logarithm, etc. (for a list of NumPy function see here); also, the advanced array functions available in NumPy can be used in Band calc for calculating vegetation indices and creating complex expressions (with the prefix np.); for instance the expression np.where("raster1" > 1, 1, 0)creates a new raster having value 1 where the input raster (i.e. "raster1") is greater than 1 and 0 where input is not greater than 1, which is useful for creating masks (for more information about NumPy function "Where" see here).
The expression can use the file name of the band or the variable name (e.g. "raster1") assigned automatically. Also, the use of the variable "bandset#b" (e.g. "bandset#b1") is accepted where b is the band number of the band set defined in the tab Band set. For instance, NDVI can be easily calculated as ("bandset#b4" - "bandset#b3")/ ("bandset#b4" + "bandset#b3") . Also, it is possible to calculate multiple rasters at once by entering multiple expressions (separated by new line) such as:
"raster1" * "raster2"
"raster3" * "raster4"
that will produce one raster for "raster1" * "raster2" and another one for "raster3" * "raster4".
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The spectral signature plot allows for the calculation spectral distances (i.e. separability) among signatures, such as: Jeffrey-Matusita distance [0 = identical, 2 = different], Spectral angle [0 = identical, 90 = different], Euclidean distance [distance in n-dimension space], Bray-Curtis similarity [0 = different, 100 = identical]. Very similar signatures are highlighted with red values.
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The Landsat pre processing tool allows for editing the metadata, which is automatically imported from the MTL file if available, in order to convert DN to reflectance. If the MTL file is not found, a list of bands is created and it is possible to insert manually the required data, which is useful for old Landsat images that have different or no metadata. Also, it is possible to remove bands from the conversion list.
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The expression can use the file name of the band or the variable name (e.g. "raster1") assigned automatically. Also, the use of the variable "bandset#b" (e.g. "bandset#b1") is accepted where b is the band number of the band set defined in the tab Band set. For instance, NDVI can be easily calculated as ("bandset#b4" - "bandset#b3")/ ("bandset#b4" + "bandset#b3") . Also, it is possible to calculate multiple rasters at once by entering multiple expressions (separated by new line) such as:
"raster1" * "raster2"
"raster3" * "raster4"
New tool Band calc (example of NDVI calculation)
The spectral signature plot allows for the calculation spectral distances (i.e. separability) among signatures, such as: Jeffrey-Matusita distance [0 = identical, 2 = different], Spectral angle [0 = identical, 90 = different], Euclidean distance [distance in n-dimension space], Bray-Curtis similarity [0 = different, 100 = identical]. Very similar signatures are highlighted with red values.
Calculation of signature distances (similar signatures in red)
Landsat conversion parameters from the metadata file
The main changes of the previous beta versions are summarized in the following video.
Please, remember that a Facebook group and a Google+ Community are available for sharing information and asking for help about the Semi-Automatic Classification Plugin.
The main changes of the previous beta versions are summarized in the following video.
Please, remember that a Facebook group and a Google+ Community are available for sharing information and asking for help about the Semi-Automatic Classification Plugin.