This task performs a matched filter supervised classification. See Matched Filtering for details.
Example
This example performs the following steps:
- Opens an AVIRIS hyperspectral image subset.
- Runs a forward minimum noise transform (MNF) to reduce noise in the data.
- Defines three regions of interest (ROIs), each containing nine pixels of a common material.
- Retrieves the spectra from the ROIs and uses their means as endmembers for matched filtering.
- Runs the MatchedFilter task.
- Displays the result. To see all of the bands, open the Data Manager. ENVI creates three MF Score images (one for each ROI) and three Infeasibility images.
e = ENVI()
File = Filepath('AVIRISReflectanceSubset.dat', $
SUBDIR=['data', 'hyperspectral'], $
ROOT_DIR=e.Root_Dir)
Raster = e.OpenRaster(File)
Task = ENVITask('ForwardMNFTransform')
Task.INPUT_RASTER = Raster
Task.Execute
Subset = ENVISubsetRaster(Task.OUTPUT_RASTER, BANDS=LINDGEN(25))
nSpectra = 9d
roi1 = ENVIROI(NAME='Green Field')
pixelAddr1 = [[77,182],[78,182],[79,182], $
[77,183],[78,183],[79,183], $
[77,184],[78,184],[79,184]]
roi1.AddPixels, pixelAddr1, SPATIALREF=Subset.SPATIALREF
roi2 = ENVIROI(NAME='Soil')
pixelAddr2 = [[386,285],[387,285],[388,285], $
[386,286],[387,286],[388,286], $
[386,287],[387,287],[388,287]]
roi2.AddPixels, pixelAddr2, SPATIALREF=Subset.SPATIALREF
roi3 = ENVIROI(NAME='Ground')
pixelAddr3 = [[296,326],[297,326],[298,326], $
[296,327],[297,327],[298,327], $
[296,328],[297,328],[298,328]]
roi3.AddPixels, pixelAddr3, SPATIALREF=Subset.SPATIALREF
spectra1 = Subset.GetData(ROI=roi1)
mean1 = Total(spectra1,1) / nSpectra
spectra2 = Subset.Getdata(ROI=roi2)
mean2 = Total(spectra2,1) / nSpectra
spectra3 = Subset.GetData(ROI=roi3)
mean3 = Total(spectra3,1) / nSpectra
endmembers = [[mean1],[mean2],[mean3]]
Task = ENVITask('MatchedFilter')
Task.INPUT_RASTER = Subset
Task.ENDMEMBERS = endmembers
Task.NAMES = ['Green Field', 'Soil', 'Ground']
Task.Execute
dataColl = e.Data
dataColl.Add, Task.OUTPUT_RASTER
View = e.GetView()
Layer = View.CreateLayer(Task.OUTPUT_RASTER)
Syntax
Result = ENVITask('MatchedFilter')
Input parameters (Set, Get): COVARIANCE, BACKGROUND_THRESHOLD, ENDMEMBERS, INPUT_RASTER, MEAN, NAMES, OUTPUT_RASTER_URI, REGULARIZATION_METHOD, REGULARIZATION_TOLERANCE, USE_SUBSPACE_BACKGROUND
Output parameters (Get only): OUTPUT_RASTER
Parameters marked as "Set" are those that you can set to specific values. You can also retrieve their current values any time. Parameters marked as "Get" are those whose values you can retrieve but not set.
Input Parameters
BACKGROUND_THRESHOLD (optional)
Specify the background threshold to use when calculating statistics using the subspace background. The default value is 0.9.
COVARIANCE (optional)
Specify an array that is the covariance matrix of the input bands. The array size is [number of bands, number of bands].
ENDMEMBERS (required)
Specify an array that is [number of bands, number of classes].
INPUT_RASTER (required)
Specify a raster on which to perform the matched filter classification.
MEAN (optional)
Specify an array that is the mean of the input bands. The number of elements in the array must match the number of bands.
NAMES (optional)
This is an array of endmember names.
OUTPUT_RASTER_URI (optional)
Specify a string with the fully qualified filename and path of the associated OUTPUT_RASTER.
- If you do not specify this parameter, or set it to an exclamation symbol (!), ENVI creates a temporary file.
- If you set it to the hash symbol (#), ENVI creates a file in the temporary directory, but this file will not be deleted when ENVI closes.
REGULARIZATION_METHOD (optional)
Specify a method for regularizing the covariance matrix:
- Diagonal: Diagonal loading, increasing all singular values by the tolerance value.
- Dominant: Dominant mode rejection, setting singular values less than the tolerance value to their mean.
- None: No regularization is used.
- Shrink: Shrinkage of singular values based on the tolerance value.
- Threshold: Singular values less than the tolerance value are set to the tolerance value.
- Truncate (default): Singular values less than the tolerance value are set to zero.
REGULARIZATION_TOLERANCE (optional)
Specify the tolerance value to use for matrix regularization. If not set, the following values will be used based on the regularization method
- Diagonal: Ten times the smallest nonzero singular value.
- Dominant: The value prescribed by Gavish & Donoho.
- None: N/A
- Shrink: The Oracle Approximating Shrinkage (OAS) estimator.
- Threshold: The largest singular value times the machine precision.
- Truncate (default): The largest singular value times the machine precision.
USE_SUBSPACE_BACKGROUND (optional)
Specify whether to use the subspace background in statistics calculation.
Output Parameters
OUTPUT_RASTER
This is a reference to the output raster of filetype ENVI.
Methods
Execute
Parameter
ParameterNames
Properties
DESCRIPTION
DISPLAY_NAME
NAME
REVISION
TAGS
Version History
ENVI 5.5 |
Introduced |
ENVI 6.2 |
Added the COVARIANCE, MEAN, REGULARIZATION_METHOD and REGULARIZATION_TOLERANCE parameters.
|
See Also
ENVITask, MixtureTunedMatchedFilter Task, ForwardMNFTransform Task, Masking Support in ENVITasks