INSMLOOK

Description

The INSMLOOK module resamples an input interferogram to create an averaged and decimated output interferogram with reduced dimensions as specified by the multi-look reduction factor. The averaging preserves the amplitude and phase characteristics of the original interferogram while the decimation in image size facilitates a reduction in the time required for phase unwrapping.

Parameters

insmlook(fili, dbic, filo, scalfact, resample)

Name	Type	Caption	Length	Value range
FILI *	str	File name of input interferogram	1 -
DBIC	List[int]	Database Input Channel List	0 -
FILO *	str	Name of Output file	1 -
SCALFACT *	List[float]	Multi-Looking Reduction Factor (X, Y)	1 - 2
RESAMPLE *	str	Resampling Method	3 -	NEAR | AVERA Default: AVERA

* Required parameter

Parameter descriptions

FILI

This parameter specifies the name of the input interferogram. The input interferogram may be generated by INSRAW, INSTOPO, INSADJUST or INSMODGOLD and should have segments containing an incidence angle array and math model.

DBIC

The input interferogram channel or channels to be multi-looked.

The default value (blank) is to multi-look all channels.

FILO

This parameter specifies the name of the file to be generated which will contain the multi-looked (averaged and decimated) output.

This file must not already exist.

SCALFACT

This parameter specifies the scale reduction factor in the X (column) and Y (row) directions. The (X, Y) scale reduction must be greater than or equal to one.

RESAMPLE

This parameter specifies the resampling method to be used for the spatial averaging which is applied before the decimation.

Details

INSMLOOK applies the user specified resampling method to the real and imaginary components of the original interferogram. The filtered output is then decimated by the user specified scale factor in the X and Y image directions.

The size of the output file is determined by the scale reduction factor(s) which can be specified as either integers or floating-point values. The number of columns and rows in the output is rounded down to the nearest integer.

To preserve the geocoding and viewing geometry information, INSMLOOK recomputes the Rational Function math model and the incidence angle array segment. Bitmaps (if any) are down sampled using the nearest neighbor resampling method. Vector segments (if any) are just transferred to the new output file. Any other segments of the input file are not transferred to the output file.

Examples

For the input interferogram with 5000 columns and 5000 rows and two channels, the following will create a two channel multi-looked output file of 3333 pixels and 1851 lines using the averaging filter.

from pci.insmlook import insmlook

fili    =   "interferogram.pix"         # original interferogram 5000 x 5000
dbic    =   []                          # default to both channels (1, 2)
filo    =   "multi-looked_averaged_interferogram.pix"   # output 3333 x 1851
scalfact   =   [1.5, 2.7]                  # output with a multilooking X, Y factors 1.5, 2.7
resample    =   "AVERA"                 # Neighborhood average method

insmlook( fili, dbic, filo, scalfact, resample )
            

Generate a multi-look interferogram from only the second channel using the nearest neighbor method and a scale reduction factor of 2 in both directions. The output file will contain a single channel of size 2500 pixels by 2500 lines.

from pci.insmlook import insmlook

fili    =   "interferogram.pix"         # original interferogram 5000 x 5000
dbic    =   [2]                         # process only second channel
filo    =   "multi-looked_nearest_interferogram.pix"    # output is 2500 x 2500
scalfact   =   [2]                         # output with a multilooking factor 2
resample    =   "NEAR"                  # Nearest neighbor method

insmlook( fili, dbic, filo, scalfact, resample )