INSPSC

Description

INSPSC generates a bitmap of pixels in the file layers specified by MFILE and/or DBIC with an amplitude dispersion index below the user specified threshold. Three raster layers containing the average amplitude, standard deviation of the amplitude, and the ratio of the standard deviation to the average amplitude (dispersion index) are also generated.

Parameters

inspsc(mfile, dbic, mask, maskfile, thres, tiledens, filo)

Name	Type	Caption	Length	Value range
MFILE*	str	Input file, folder, or text file	1 -
DBIC	List[int]	Database input channel list	0 - 1	Default: 1
MASK	List[int]	Area mask (bitmap or vector)	0 - 1
MASKFILE	str	Mask file	0 -
THRES	List[float]	Maximum Threshold for Amplitude Dispersion Index	0 - 1	Default: 0.35
TILEDENS	List[int]	Density of pixels per area	0 - 3	Default: 0
FILO*	str	Database output file name	1 -

* Required parameter

Parameter descriptions

MFILE

The name of a folder or text file that contains the coregistered (and aligned) data to be processed. The polarization and calibration type of the coregistered backscattering must match for all layers. (i.e. POLARIZATION = one of HH, HV, VH, VV, RH, RV, etc. and CALIBTYP = one of NONE, SIGMA, BETA or GAMMA). For more information about using MFILE, including the requirements for a valid file, see Using an MFILE with a CATALYST Professional algorithm.

DBIC

The input channel to be used for the calculation of the amplitude dispersion index. The default (blank) is to process the first channel.

MASK

The areas of the dataset to be excluded from the amplitude dispersion calculations. You can define exclusion areas using either bitmaps or polygon vectors. When a bitmap segment is specified, all pixels having a bitmap value of one define the area to mask. The bitmap segment must match the slant range projection of the input. When a vector mask is specified, the masked pixels are those contained within the polygons.

MASKFILE

The name of the file containing the mask, which you can specify as an option. If you do not specify a value for the MASK and MASKFILE parameters, no masking is performed. You cannot use the default value of MASK when MASKFILE is explicitly specified. MASKFILE is expected to be in a slant range projection of input files.

THRES

This parameter specifies the maximum value of the amplitude dispersion index to be used for the identification of permanent scatterers. The threshold value must be greater than zero. The default value is 0.35

TILEDENS

Sets a maximum pixel count allowed per given rectangular area. Areas with more than N PSC pixels are reduced to the N best ADI values. DENSITY is an optional feature and can be blank or set to [0] to disable. Order positions as follows:

1st: Max pixels in rectangular area. 0 = disable feature

2nd: Width of rectangular area in Pixels. Width and Height if 3rd left undefined

3rd: Height of rectangular area.

FILO

This file must not already exist.

Details

The INSPSC module processes a stack of coregistered SAR images to identify stable reflectors (permanent scattering candidates) generally containing a single dominant scattering mechanism which is only marginally affected by temporal and geometric decorrelation. These stable points can be utilized to estimate and remove atmospheric artifacts from a stack of interferograms.

Persistent scatterers are identified by examining the temporal characteristics of a specific pixel's backscattering signal to determine the amplitude dispersion index. The amplitude dispersion index for each pixel is defined as the standard deviation of the amplitude divided by the mean amplitude. Pixels with a dispersion index less than the user defined threshold are identified as persistent scatterer candidates.

The input stack specified by the MFILE parameter must point to coregistered data sets all calibrated in a similar manner with identical polarization.

Examples

Generate a bitmap for all pixels with an amplitude dispersion less than or equal to the default value of 0.35 from the first channel for the coregistered files listed in the text file specified by the MFILE parameter.

from pci.inspsc import inspsc

mfile   =  r"c:/InSAR_Stack.txt"    #text file listing coregistered files
dbic    =  []                       #process default (first layer)
mask    =  []                       #no exclusion mask is used
maskfile = ""                       #no mask file is required
thres    =  []                      #default value of 0.35 used
density =  []                       #disabled feature
filo    =  r"c:/PSC.pix"            #output containing bitmap and raster layers

inspsc(mfile, dbic, mask, maskfile, thres, density, filo)
        

Generate a bitmap for all pixels with an amplitude dispersion less than or equal to 0.4 for areas outside the polygons delineated by segment 3 of the mask file. The amplitude dispersion will be calculated using the backscattering amplitude from channel 2 for the files listed in the text file given by the MFILE parameter.

from pci.inspsc import inspsc

mfile   =  r"c:/InSAR_Stack.txt"    #text file listing coregistered files
dbic    =  [2]                      #process the second layer in the files
mask    =  [3]                      #exclude polygons in segment 3
maskfile = r"c:/Maskfile.pix"       #name of file containing masks
thres   =  [0.4]                    #select pixels with dispersion 0 to 0.4
density =  []                       #disabled feature
filo    =  r"c:/PSC_Mask.pix"       #output containing point vectors

inspsc(mfile, dbic, mask, maskfile, thres, density, filo)
      

Acknowledgements

The PCI Interferometric SAR (InSAR) project was funded in part by the Canadian Space Agency under the Earth Observation Application Development Program (EOADP) contract (9F043-130644/006/MTB), Application Development for Environmental Monitoring and Remediation.