CalculateQUACGainOffset Task

This task calculates the gain and offset for QUick Atmospheric Correction (QUAC) on multispectral or hyperspectral imagery.

Note: This function 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('qb_boulder_msi', Subdir=['data'], $

Root_Dir=e.Root_Dir)

Raster = e.OpenRaster(File)

; Get the task from the catalog of ENVITasks

Task = ENVITask('CalculateQUACGainOffset')

; Define inputs

Task.INPUT_RASTER = Raster

; Run the task

Task.Execute

; Print the bad bands list, gains, and offsets

Print, 'Bad bands: ',Task.BBL

Print, 'Gains: ',Task.GAIN

Print, 'Offsets: ',Task.OFFSET

Result:

Bad bands: 1 1 1 1

Gains: 0.0012088706 0.00075686112 0.00098287757 0.00099052524

Offsets: -0.18737493 -0.13812715 -0.093373366 -0.053983625

Syntax

Result = ENVITask('CalculateQUACGainOffset')

Input properties (Set, Get): INPUT_RASTER, SENSOR

Output properties (Get only): BBL, GAIN, OFFSET

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

BBL

This is the bad band list, returned as a byte array in the form of [number of bands]. A value of 1 indicates a good band, and 0 indicates a bad band.

GAIN

This parameter contains the data gain values that can be applied to the raster, returned as a double-precision array in the form of [number of bands].

INPUT_RASTER (required)

Specify a raster to calculate the gain and offset for QUick Atmospheric Correction (QUAC).

OFFSET

This parameter contains the data offset values that can be applied to the raster, returned as a double-precision array in the form of [number of bands].

SENSOR (optional)

Specify one of the following strings, indicating the sensor type of the input raster:

Generic / Unknown Sensor

Highly Vegetated Scenes

AISA-ES

ALI

ASAS

AVIRIS

CAP ARCHER

CASI

COMPASS

HYCAS

HYDICE

HyMap

Hyperion

Landsat TM/ETM/OLI

LASH

MARS

MODIS

QuickBird

RGB

WorldView-2

Near Infrared (NIR)

Near-Shortwave Infrared (NIR-SWIR)

If SENSOR is not set, then the task uses the Generic/Unknown Sensor option to guess the best sensor type, based on the number of input bands and their wavelengths.
Select the Highly Vegetated Scenes option if the image is highly vegetated.
Select the Near Infrared (NIR) option if the input raster has more than 70 bands and the wavelengths span the near-infrared region.
Select the Near-Shortwave Infrared (NIR-SWIR) option if the input raster has more than five bands and the wavelengths span the near-shortwave infrared region.

Version History

ENVI 5.3

Introduced

API Version

4.2