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ENVIRadiometricCalibrationTask

ENVIRadiometricCalibrationTask

This task calibrates an image to radiance, top-of-atmosphere reflectance, or brightness temperatures. See Radiometric Calibration for a list of sensors and their calibration options. To process a spatial or spectral subset instead of the entire image, use ENVISubsetRaster before calling the ENVITask.

Note: Use ENVIApplyGainOffsetTask to apply custom gains and offsets to a raster that will be input to a custom calibration routine. Do not pass the output of ENVIApplyGainOffsetTask to ENVIRadiometricCalibrationTask.

The virtual raster associated with this task is ENVICalibrateRaster.

Example


This example shows how to add custom gain/offset metadata to a QuickBird image, then calibrate it to radiance in units of W/(m2 * sr * µm).

; 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)
 
; Define gains and offsets for a QuickBird file saved
; to ENVI format
Gains = [0.21044118, 0.10555556, 0.13633803, 0.13754386]
Offsets = [0.0, 0.0, 0.0, 0.0]
Metadata = Raster.Metadata
Metadata.AddItem,'data gain values', Gains
Metadata.AddItem,'data offset values', Offsets
 
; Process a spectral subset of Band 2
Subset = ENVISubsetRaster(Raster, Bands=[1])
 
; Get the radiometric calibration task from the catalog of ENVI tasks
Task = ENVITask('RadiometricCalibration')
 
; Define inputs. Since radiance is the default calibration
; method, we do not need to specify it here.
Task.INPUT_RASTER = Subset
Task.OUTPUT_DATA_TYPE = 'Double'
 
; Run the task
Task.Execute
 
; Get the collection of data objects currently available in the Data Manager
DataColl = e.Data
 
; Add the output to the Data Manager
DataColl.Add, Task.OUTPUT_RASTER
 
; Display the result
View = e.GetView()
Layer = View.CreateLayer(Task.OUTPUT_RASTER)

Syntax


Result = ENVITask('RadiometricCalibration')

Input properties (Set, Get): INPUT_RASTER, CALIBRATION_TYPE, SCALE_FACTOR, OUTPUT_DATA_TYPE, OUTPUT_RASTER_URI

Output properties (Get only): OUTPUT_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:

AddParameter

Execute

Parameter

ParameterNames

RemoveParameter

Properties


This task inherits the following properties from ENVITask:

COMMUTE_ON_DOWNSAMPLE

COMMUTE_ON_SUBSET

DESCRIPTION

DISPLAY_NAME

NAME

REVISION

TAGS

This task also contains the following properties:

CALIBRATION_TYPE (optional)

Specify a string indicating the calibration type:

  • Radiance (default)
  • Top-of-Atmosphere Reflectance
  • Brightness Temperature

See the Radiometric Calibration tool instructions for detailed definitions and units for each option.

INPUT_RASTER (required)

Specify a raster on which to perform radiometric calibration.

OUTPUT_DATA_TYPE (optional)

Specify a string indicating the output data type:

  • Int: 16-bit integer
  • Float: Floating-point (default)
  • Double: Double-precision floating point
  • UInt: 16-bit unsigned integer

OUTPUT_RASTER

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

OUTPUT_RASTER_URI (required)

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.

SCALE_FACTOR (optional)

This keyword pertains to radiance only. To output radiance in different units than W/(m2 * sr * µm), enter a floating-point scale factor to get the calibrated image in your desired units. If you do not specify this keyword, the default value scale factor is 1.0 which will yield a radiance image in units of W/(m2 * sr * µm).

Version History


ENVI 5.1

Introduced

ENVI 5.2

The CALIBRATION_TYPE and OUTPUT_DATA_TYPE properties use string values instead of integers.

API Version


3.3

See Also


ENVITask, ENVITask::Parameter, ENVICalibrateRaster, ENVISubsetRaster



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