This function constructs an ENVIRaster from a radar amplitude source raster that has been calibrated to sigma nought backscatter, in decibels. It currently only works with ALOS-1 or ALOS-2 PALSAR Level-1.5, 2.5, and 3.1 data.

The result is a virtual raster, which has some additional considerations with regard to methods and properties. See Virtual Rasters for more information, including how they differ from ENVITasks.

The equivalent task is RadarBackscatter.


This example shows how to calibrate an ALOS-2 PALSAR Level-1.5 ScanSAR product.

; Start the application
e = ENVI()
; Open an ALOS-2 PALSAR file
file = 'LED-ALOS2404053250-200622-WBDL1.5GUD'
raster = e.OpenRaster(file)
; Calibrate the image to sigma nought
CalibratedImage = ENVIRadarBackscatterRaster(raster)
; save it in ENVI raster format
newFile = e.GetTemporaryFilename()
CalibratedImage.Export, newFile, 'ENVI'
; Open the image
CalibratedImage = e.OpenRaster(newFile)
; Display the result
View = e.GetView()
Layer = View.CreateLayer(CalibratedImage)


Result = ENVIRadarBackscatterRaster(Input_Raster, ERROR=variable])

Return Value

This routine returns a reference to an ENVIRaster.



Specify the input ENVIRaster.


This virtual raster inherits methods and properties from ENVIRaster; however the following methods will override the ENVIRaster methods:




ERROR (optional)

Set this keyword to a named variable that will contain any error message issued during execution of this routine. If no error occurs, the ERROR variable will be set to a null string (''). If an error occurs and the routine is a function, then the function result will be undefined.

When this keyword is not set and an error occurs, ENVI returns to the caller and execution halts. In this case, the error message is contained within !ERROR_STATE and can be caught using IDL's CATCH routine. See IDL Help for more information on !ERROR_STATE and CATCH.

See Manage Errors for more information on error handling in ENVI programming.


Specify a string that identifies the raster.

Version History

ENVI 5.2.1


ENVI 5.3.1

Documented the dehydrated form of this virtual raster

ENVI 5.4

Added the Dehydrate and Hydrate methods; added NAME keyword

API Version


See Also

ENVIRaster, RadarBackscatter Task