INSCOREG

Description

INSCOREG automatically coregisters and resamples a dependent file to a reference file. Control points are acquired automatically, outliers removed, and pixels resampled to match the reference file. The metadata of the resampled output file is updated to reflect the modified geolocation information. Non-overlapping areas are flagged as NoData.

Parameters

Name	Type	Length	Value range
InputRef: Reference image *	Raster port	1 - 1
InputDep: Dependant image *	Raster port	1 - 1
Input: Images to coregister	Raster port	0 - 1
MODELTYP	String	0 -
Number of Candidate GCPs	Integer	0 - 1	1 - Default: 500
Minimum correlation score	Float	0 - 1	0.72 - 1 Default: 0.75
Search radius (in pixels)	Integer	0 - 1
Report	String	0 - 192	See parameter description

* Required parameter

Parameter descriptions

InputRef: Reference image

The name of the file to use as the reference data set.

InputDep: Dependant image

The name of the file to use as the dependant data set.

Input: Images to coregister

The name of the file to resample and coregister.

MODELTYP

The type of model to fit to the collected GCPs, the model is then used to interpolate pixel shifts between GCPs. The valid options are:

• TPS: Apply a thin plate spline
• POLY#: Apply polynomial model, you can add a number after to specify the order

The default is a 2nd order polynomial model.

Number of Candidate GCPs

The number of grid points to distribute over the reference image. The corresponding location, based on geocoding information, is used as the center of the search radius in the dependent file.

The value must be greater than or equal to 1. The default value is 500.

Minimum correlation score

The minimum acceptable correlation score. Match points with a lower correlation score will be rejected. The value must be in the range of 0 (no correlation) to 1 (perfect correlation). The default value is 0.75, and is the recommended minimum value.

Search radius (in pixels)

The search radius, in pixels, to examine to find a match between the reference and dependent images. The value must be greater than or equal to 1. The default value is 50.

Report

Specifies where to direct the generated report.

Available options are:

• LOG: generates a report on the terminal (default)
• <modulename.RPT>: appends a report to the module's RPT file
• DISK: generates a report on file "IMPRPT.LST"

Details

The reference channel and the dependent channel you specify are used to generate image match points. The number of candidate points you specify are distributed evenly (in a grid) over the reference image. With each candidate reference point, a corresponding location in the dependent file is determined. The area surrounding the dependent location is scanned to find the image match with the highest score.

Dependent points with a correlation below the threshold you specify are removed. The remaining match points are used to derive the mapping of the low-order-polynomial, which is applied to all channels specified in the input channel list. The resampled complex-valued output contains the number of channels, and the order of occurrence, corresponding to the input channel list.

Algorithm

Points with an absolute error of less than 0.1 of a pixel in both the x and y directions are stored as ground control points (GCP). The transformation determines the exact image location of the output pixel. INSCOREG applies a transformation of the second-order polynomial to the dependent data. If less than 10 GCPs are found, the order of the polynomial transformation is reduced to one; that is, an affine transformation is applied.

The value of the output pixel is determined by using a two-dimensional sinc function; that is, sin (x)/x), as the resampling kernel over a 16-by-16 neighborhood.

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.