FLAASH Task

This task performs Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes (FLAASH) on multispectral or hyperspectral imagery.

This task requires a separate license for the ENVI Atmospheric Correction Module; contact your sales representative for more information.

Example

;Start the application

e = ENVI()

;Open an input file

File = Filepath('AVIRISReflectanceSubset.dat', Subdir=['data', 'hyperspectral'], $

  Root_Dir=e.Root_Dir)

Raster = e.OpenRaster(File)

;Get the task from the catalog of ENVITasks

Task = ENVITask('FLAASH')

;Define inputs

Task.INPUT_RASTER = Raster

Task.INPUT_SCALE = 1

;Run the task

Task.Execute

;Add the output to the Data Manager

e.Data.Add, Task.OUTPUT_RASTER

;Display the result

View = e.GetView()

Layer = View.CreateLayer(Task.OUTPUT_RASTER)

Syntax

Result = ENVITask('FLAASH')

Input properties (Set, Get): AEROSOL_SCALE_HT, AER_BANDHIGH_MAXREFL, AER_BANDHIGH_WAVL, AER_BANDLOW_MAXREFL, AER_BANDLOW_WAVL, AER_BAND_RATIO, AER_BAND_WAVL, AER_REFERENCE_PIXEL, AER_REFERENCE_VALUE, CALIBRATION_FILE, CALIBRATION_FORMAT, CALIBRATION_UNITS, CLOUD_RASTER_URI, CO2_MIXING, DATE_TIME, DEFAULT_VISIBILITY, GROUND_ELEVATION, IFOV, INPUT_RASTER, INPUT_SCALE, LAT_LONG, LOS_AZIMUTH, LOS_ZENITH, MODTRAN_AER, MODTRAN_ATM, MODTRAN_MSCAT, MODTRAN_RES, OUTPUT_RASTER_URI, OUTPUT_SCALE, POLISHING_RESOLUTION, SENSOR_ALTITUDE, SENSOR_AUTOCALIBRATION, SENSOR_CAL_FEATURE_LIST, SENSOR_CAL_PRECISION, SENSOR_TYPE, SOLAR_AZIMUTH, SOLAR_ZENITH, USE_ADJACENCY, USE_AEROSOL, USE_POLISHING, WATER_ABS_CHOICE, WATER_MULT, WATER_RASTER_URI, WATER_VAPOR_PRESET

Output properties (Get only): CLOUD_RASTER, OUTPUT_RASTER, WATER_RASTER

Properties marked as "Set" are those that you can set to specific values. You can also retrieve their current values any time. Properties marked as "Get" are those whose values you can retrieve but not set.

Methods

This task inherits the following methods from ENVITask:

Properties

This task inherits the following properties from ENVITask:

COMMUTE_ON_DOWNSAMPLE

AEROSOL_SCALE_HT (optional)

Adjust the scattering range for adjacency correction. Specify the highest altitude in kilometers of the boundary aerosol layer. The default value is 2.

AER_BANDHIGH_MAXREFL (optional)

Specify a maximum reflectance threshold for the upper band of the custom 2-band aerosol retrieval. Pixels brighter than this value will be excluded from the aerosol retrieval process.

AER_BANDHIGH_WAVL (optional)

Specify wavelengths [nanometers] for the upper band of the custom 2-band aerosol retrieval. Specify a single wavelength or an interval.

AER_BANDLOW_MAXREFL (optional)

Specify the maximum reflectance threshold for the lower band of the custom 2-band aerosol retrieval. Pixels brighter than this value will be excluded from the aerosol retrieval process.

AER_BANDLOW_WAVL (optional)

Specify wavelengths [nanometers] for the lower band of the custom 2-band aerosol retrieval. Specify a single wavelength or an interval.

AER_BAND_RATIO (optional)

Specify a target ratio of reflectance values between two bands for the custom 2-band aerosol retrieval.

AER_BAND_WAVL (optional)

Specify wavelengths [nanometers] for the band of the custom single-band aerosol retrieval. Specify a single wavelength or an interval.

AER_REFERENCE_PIXEL (optional)

Specify the location of a pixel (column, line) to use in the single band aerosol retrieval. If undefined, the darkest in-band pixel will be used as a reference.

AER_REFERENCE_VALUE (optional)

Specify the expected reflectance value of a pixel to use in the single band aerosol retrieval. This is primarily useful when a known target material is present. The default value is 0.

CALIBRATION_FILE (optional)

Specify a full path and filename for sensor wavelength calibration data. The file should contain the following:

ASCII: two column text file which specifies channel center and width values.
Discrete: Text file defining channel shapes as paired wavelength and response values.
ENVI: ENVI-style cube header with wavelength, fwhm, and bbl arrays.
Filter Format: Filter file (.sli) containing discrete channel shape data as an array of wavelengths vs response in consecutive order, one for each band of the sensor.
Spectograph: Text file that contains spectrograph definitions, and optionally may contain features to use in sensor autocalibration.

CALIBRATION_FORMAT (optional)

Set the sensor calibration file format with one of the following:

ASCII
Discrete
ENVI
Filter Format
FLAASH (default)
Spectograph

For FLAASH, sensor calibration data is defined within the FLAASH input configuration. For all other selections, you must also specify a CALIBRATION_FILE.

CALIBRATION_UNITS (optional)

If a CALIBRATION_FILE was added, specify the wavelength units of the calibration data. Valid values are:

nanometers
microns

CLOUD_RASTER

This is a reference to the cloud output raster of filetype ENVI.

CLOUD_RASTER_URI (optional)

Specify a string with the fully qualified filename and path of the associated CLOUD_RASTER. If you do not set this parameter to a valid filename, a cloud raster will not be generated.

CO2_MIXING (optional)

Sets a CO2 mixing ratio in ppmv. If omitted, a default value is estimated for the year of the acquisition based on historical trends.

DATE_TIME (optional)

Specify the collection date and time of the image as [YYYY,MM,DD,H,M,S]. Time is given in GMT.

DEFAULT_VISIBILITY (optional)

Set a default visibility in kilometers for the scene. If the aerosol retrieval is disabled, the default visibility is used; otherwise, the default visibility is used only for the first water retrieval. The default value is 40.

GROUND_ELEVATION (optional)

Specify the average ground elevation, in kilometers.

IFOV (optional)

(Instantaneous Field of View) Specify the angle of individual sensors, in milliradians.

INPUT_RASTER (required)

Specify a raster on which to perform atmospheric correction.

INPUT_SCALE (optional)

Specify the band normalization factors that convert the pixel values in the input raster into uW/cm2/nm/sr.

LAT_LONG (optional)

Specify the Latitude and Longitude of the scene center, in decimal degrees.

LOS_AZIMUTH (optional)

Specify the line-of-sight azimuth angle for a non-nadir data acquisition. The azimuth angle is measured as degrees clockwise from North to the line-of-sight vector (90 degrees due east, -90 degrees due west). The default value is 0.

LOS_ZENITH (optional)

Specify the line-of-sight zenith angle in degrees for a non-nadir data acquisition. For a nadir viewing instrument this angle is 180 degrees. The default value is 180.

MODTRAN_AER (optional)

Set the MODTRAN aerosol model with one of the following:

No Aerosol
High-Visibility Rural: (default) (visibility = 23 Km)
Low-Visibility Rural: (visibility = 5 Km)
Maritime: (visibility = 23 Km)
Tropospheric: (visibility = 50 Km)
Urban

MODTRAN_ATM (optional)

Set the MODTRAN atmospheric model.

Tropical Atmosphere: (default) (15 degrees north latitude)
Mid-Latitude Summer: (45 degrees north latitude)
Mid-Latitude Winter: (45 degrees north latitude)
Sub-Arctic Summer: (60 degrees north latitude)
Sub-Arctic Winter: (60 degrees north latitude)
1976 US Standard Atmosphere

MODTRAN_MSCAT (optional)

Selects a multiple scattering method to use in MODTRAN. ISAACS (fastest), Scaled ISAACS (fast, more accurate), DISORT (SLOW, most accurate).

The default value is Scaled ISAACS.

ISAACS: The fastest method.
DISORT: The slowest method, but is the most accurate.
Scaled ISAACS: (default) Fast, more accurate than ISAACS.

MODTRAN_RES (optional)

Specify the bandmodel resolution to use with the MODTRAN simulations with one of the following:

15.0 (default)
5.0
1.0
0.1

OUTPUT_RASTER

This is a reference to the output raster of filetype ENVI.

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 property, or set it to an exclamation symbol (!), a temporary file will be created.

OUTPUT_SCALE (optional)

Specify a multiplier to rescale reflectance values [0,1] to integer values in the output. Output reflectances are always written as short integers.

POLISHING_RESOLUTION (optional)

Width of the smoothing filter (in bands) used for the spectral polishing. An odd number is recommended for performance reasons. A number equivalent to the spectral width between 50 and 200 nm is also recommended.

SENSOR_ALTITUDE (optional)

Specify the sensor altitude, in kilometers.

SENSOR_AUTOCALIBRATION (optional)

Specify true or false to enable or disable sensor auto-calibration (NODD) algorithm. This also activates the automated smile correction for appropriate sensors. This calibration is not compatible with MSI sensor types. The default is false.

SENSOR_CAL_FEATURE_LIST (optional)

Specify a set of spectral features used to adjust sensor calibration when Sensor Autocalibration is active. All features are selected by default. In the following list of features, the first three are the most reliable based on past performance. O2_763, H2O_940, CO2_2040, Solar_H_434, Solar_H_486, Solar_Mg_517, Solar_H_656, O2_691, H2O_820, H2O_1130, O2_1266, CO2_1614.

SENSOR_CAL_PRECISION (optional)

Set a minimum accuracy threshold for the sensor autocalibration. This parameter determines whether or not a spectral absorption feature will contribute to the calibration adjustment, based on the variance of the estimated wavelength shift local to that feature. The default value is 0.150000.

SENSOR_TYPE (optional)

Set the name of the sensor as one of the following:

AVIRIS
HYDICE
HyMap
Hyperion
NVIS
Compass
Hycas
Mars
Multispectral
Unknown (default)

SOLAR_AZIMUTH (optional)

Specify the relative solar angle as measured from the ground at the imaged site. The azimuth angle is measured as degrees clockwise from north to the line of sight vector of the sun. The default value is -1.

SOLAR_ZENITH (optional)

The relative solar angle as measured from the ground at the imaged site. A zenith angle of 0 is directly overhead, 90 is on the horizon. The default value is -1.

USE_ADJACENCY (optional)

Enable or disable compensation for adjacency effects with one of the following:

Disabled
Legacy exponential scattering kernel
Wavelength-dependent scattering kernel (default)

USE_AEROSOL (optional)

Enable or disable an aerosol retrieval algorithm to obtain a scene visibility with one of the following:

Disabled
Automated Selection (default)
Vegetation Based Retrieval
Water Based Retrieval
Wavelength Dependent Water Based Retrieval
Linear Regression Retrieval

USE_POLISHING (optional)

Specify whether to enable or disable spectral polishing with one of the following. Polishing is incompatible with MSI sensors.

Disabled (default)
Polish using reference materials
Polish using statistical detection of spectral artifacts

WATER_ABS_CHOICE (optional)

Set the water absorption feature to use with the water vapor retrieval with one of the following"

1130
940
820
Automated Selection (default)

WATER_MULT (optional)

Specify the minimum and maximum water column multiplier for selected MODTRAN atmosphere. The default value is 0.0100000.

WATER_RASTER (optional)

This is a reference to the water vapor output raster of filetype ENVI.

WATER_RASTER_URI (optional)

Specify a string with the fully qualified filename and path of the associated WATER_RASTER. If you do not set this parameter to a valid filename, a water vapor raster will not be generated.

WATER_VAPOR_PRESET (optional)

Specify a value to override the water retrieval with a constant scale factor. A positive value will disable the water vapor retrieval. The default value is 0.

Version History

ENVI 5.7	Introduced
ENVI 6.0	CALIBRATION_FILE will accept a filter function file when CALIBRATION_FORMAT is Filter Format.

API Version

4.2