Description
INSRAW creates a raw interferogram using coregistered reference and dependent data sets. INSRAW supports the following coregistration configurations:
- i. dependent file resampled to the reference file
- ii. reference file resampled to the dependent file
- iii. reference and dependent resampled to a third slant range file.
All resampling must be performed by the INSCOREG module.
You can, as an option, filter the interferogram by using an adaptive Lee filter.
Parameter descriptions
DBIC_REF
The list of channel numbers from the reference file.
InputRef: Reference image
The list of channel numbers to use as the reference data set.
InputDep: Resampled dependent file
The list of channel numbers from the dependent file. The number of channels must match identically with the number in the reference file.
ApplyFilter
Select this check box to apply an adaptive Lee filter to the interferogram. When you select this check box, you must also type or select a value for Filter size.
Filter size (pixels)
The filter size, in pixels, of the adaptive Lee filter to apply. You specify the filter as n x n, where
n is an odd integer greater than or equal to five.
Output: Output raw interferogram
The name of the output file to which to write the raw interferograms. The file will contain the same number of pixels and lines as the reference file and the number of channels you specified. Nonoverlapping areas will be processed as NoData. The file name you specify must not exist already.
Details
The dependent file must be coregistered and aligned (by running the INSCOREG algorithm) pixel-by-pixel with the reference file. Both the reference and resampled dependent file must be in single-look complex format (SLC), and the beam modes must be the same. The output file will contain the same number of pixels and lines as the reference file with the number of complex valued channels you specified. Each output channel represents the interferometric product of the corresponding input channels.
Note: The value of DBIC_REF and DBIC need not be identical.
Viewing unfiltered interferograms in CATALYST Professional
Focus
In
Focus, the default interpretation of complex values is
Intensity. If you opted not to use the adaptive Lee filter, the interferometric phase is computed without filtering (i.e. 1x1), but the resulting interferogram will have the magnitude (and intensity) associated with the minimum 5x5 filter. This is to avoid generating an interferogram with a constant coherence (amplitude) value of one. If you want to view unfiltered interferograms in
Focus, open the file, and then do either of the following:
- On the Maps tab, right-click the unfiltered interferogram you want to display, point to Data Interpretation, and then click Phase in radians or Phase in degrees, as applicable.
- On the Files tab, expand Rasters, right-click the channel you want, point to View, and then click As Amplitude and Phase.
Algorithm
The following formula is the complex-valued correlation coefficient of the input reference and dependent files, where w
i is the weight of the adaptive Lee Filter, I
k
ref and I
k
dep are the complex values of the references and coregistered dependent data for the k
th channel listed in reference and dependent files, respectively, * is the complex conjugate, and N is the size of the adaptive filter. If N = 1, then |γ
raw| = 1.
The magnitude of the correlation coefficient is the coherence of the interferogram. Typically, a higher coherence represents a higher-quality interferogram. The magnitude of a complex number is computed as follows:
The phase of the correlation coefficient is the relevant wrapped interferometric phase. The phase of a complex number is computed as follows:
