INSTEMPORALCOH

Description

INSTEMPORALCOH is used to identify regions of high temporal coherence (persistent scatterers). This is accomplished by minimizing the difference between the wrapped phase and the expected phase associated with a given range of velocities and topographical errors. The input consists of a stack of co-registered interferograms.

Parameters

instemporalcoh(mfile, dbic, pixelpos, filo)

Name	Type	Caption	Length	Value range
MFILE*	str	Input folder, or text file	1 -
DBIC	List[int]	Input raster channel	0 -	Default: 1
PIXELPOS*	List[int]	Reference Location in pix files	2 -
FILO*	str	Database output file name	1 -

* Required parameter

Parameter descriptions

MFILE

The name of a folder, or a text file that contains the input images to process. Only the PIX file format (*.pix) is supported.

All input files must be co-registered and have the same number of lines and columns.

When MFILE is a text file, it must contain a list of files (one per line) with their full pathname, for example: MFILE="C:/change_detection/sarimage_list.txt"

where the text file contains full path file names.

C:/change_detection/sarimage_20201028.pix C:/change_detection/sarimage_20201121.pix C:/change_detection/sarimage_20201215.pix C:/change_detection/sarimage_20201009.pix C:/change_detection/sarimage_20201126.pix

Alternatively, an input folder can be specified: MFILE = "C:\change_detection"

The use of wildcards (*) is recommended to refine the search within the specified folder, for example:

MFILE = r"C:\InSAR_project\RAW\*.pix"

MFILE = r"C:\InSAR_project\RAW\ref*.pix"

DBIC

All input channels must be of the same size (lines, columns) and type.

PIXELPOS

Specifies location of stationary reference point in image [pixel, line].

FILO

Specifies the name of the PIX file to be generated.

This file must not already exist.

Details

SAR TEMPORAL COHERENCE ESTIMATION

The phase of the user specified reference point is used to remove the random offset for each layer. The adjusted phase values are then temporally ordered. For each pixel and time interval, the module computes the temporal coherence by summing the normalized circular phase differences between the modeled phase for a given velocity and topographic error with the wrapped phases extracted from the phase adjusted stack. An iterative gradient search technique is used to converge to the nominal velocity and topographic error required to maximize the temporal coherence. The temporal coherence, nominal velocity, and topographic error are written to the output file. Pixels with a high temporal coherence value generally delineate stable regions containing reliable estimates.

Example

Calculate the temporal coherence, nominal velocity, and topographic error from a coregistered stack of interferograms where the image location of a stationary point is known.

from pci.instemporalcoh import instemporalcoh

mfile    =  "C:/mfile.txt"            #Text file with list of interferograms
dbic	 = []                           #select default 1st channel
PIXELPOS =	[1000,2000]               #Pixel location reference point
filo     =  r"C:/INSTEMPORALCOH.pix"  #output file

instemporalcoh(mfile, dbic, PIXELPOS, filo)