other versions
- jessie 6.4.4-1
- stretch 7.2.0-2
- testing 7.6.0-1
- unstable 7.6.0-1
- experimental 7.6.1-1~exp1
i.maxlik(1grass) | Grass User's Manual | i.maxlik(1grass) |
NAME¶
i.maxlik - Classifies the cell spectral reflectances in imagery data.KEYWORDS¶
imagery, classification, MLCSYNOPSIS¶
i.maxlikFlags:¶
- -q
-
- --overwrite
-
- --verbose
-
- --quiet
-
Parameters:¶
- group=name
-
- subgroup=name
-
- sigfile=name
-
- class=name
-
- reject=name
-
DESCRIPTION¶
i.maxlik is a maximum-likelihood discriminant analysis classifier. It can be used to perform the second step in either an unsupervised or a supervised image classification. Either image classification methods are performed in two steps. The first step in an unsupervised image classification is performed by i.cluster; the first step in a supervised classification is executed by the GRASS program i.class. In both cases, the second step in the image classification procedure is performed by i.maxlik. In an unsupervised classification, the maximum-likelihood classifier uses the cluster means and covariance matrices from the i.cluster signature file to determine to which category (spectral class) each cell in the image has the highest probability of belonging. In a supervised image classification, the maximum-likelihood classifier uses the region means and covariance matrices from the spectral signature file generated by i.class, based on regions (groups of image pixels) chosen by the user, to determine to which category each cell in the image has the highest probability of belonging. In either case, the raster map layer output by i.maxlik is a classified image in which each cell has been assigned to a spectral class (i.e., a category). The spectral classes (categories) can be related to specific land cover types on the ground. The program will run non-interactively if the user specifies the names of raster map layers, i.e., group and subgroup names, seed signature file name, result classification file name, and any combination of non-required options in the command line, using the form i.maxlik[-q] group=name subgroup=name sigfile=name class=name [ reject=name] where each flag and options have the meanings stated below. Alternatively, the user can simply type i.maxlik in the command line without program arguments. In this case the user will be prompted for the program parameter settings; the program will run foreground.OPTIONS¶
Parameters:¶
- group=name
-
- subgroup=name
-
- sigfile=name
-
- class=name
-
- reject=name
-
NOTES¶
The maximum-likelihood classifier assumes that the spectral signatures for each class (category) in each band file are normally distributed (i.e., Gaussian in nature). Algorithms, such as i.cluster, i.class, or i.gensig, however, can create signatures that are not valid distributed (more likely with i.class). If this occurs, i.maxlik will reject them and display a warning message. This program runs interactively if the user types i.maxlik only. If the user types i.maxlik along with all required options, it will overwrite the classified raster map without prompting if this map existed.EXAMPLE¶
Completion of the unsupervised classification of a LANDSAT subscene (VIZ, NIR, MIR channels) in North Carolina (see i.cluster manual page for the first part):class=lsat7_2002_clust_classes reject=lsat7_2002_clust_classes.rej
SEE ALSO¶
The GRASS 4 Image Processing manual i.class, i.cluster, i.gensig, i.group, r.kappaAUTHORS¶
Michael Shapiro, U.S.Army Construction Engineering Research LaboratoryGRASS 6.4.4 |