INSCALDEFO2

Description

INSCALDEFO2 adjusts unwrapped displacement values to GNSS points with known movements. The input raster is created by unwrapping the interferogram in deformation mode. Deformation interferograms to calibrate must be in the raw image geometry.

Parameters

Name	Type	Caption	Length	Value range
FILE*	String	Displacement file name	1 - 192
DBIC	Integer	Input displacement channel	0 - 1
DBOC	Integer	Output raster channel containing the calibrated displacements	0 - 1
FILREF*	String	File containing Delaunay segment	1 - 192
MFILE*	String	Input file, folder, or text file	1 - 192
CALWIN	Integer	Calibration window size	0 - 2
ADJMETHOD	String	Displacement adjustment method	0 - 32	AVERAGE\|MEDIAN\|PLANE Default: AVERAGE
MONITOR	String	Monitor mode	0 - 3	ON, OFF Default: ON

* Required parameter

Parameter descriptions

FILE

The name of the file containing the displacements to be calibrated. Typically, the file is an interferogram unwrapped in the deformation mode, with displacements (in meters) in a 32R channel.

DBIC

The input channel containing the displacements to calibrate.

Ranges of channels or segments can be specified with negative values. For example, {1,-4,10} is internally expanded to {1,2,3,4,10}. When you are not specifying a range in this way, only 48 numbers can be specified explicitly.

DBOC

The channel of FILE to which to write the calibrated displacement data. The channel type must be 32R.

If the output channel DBOC is the same as the input channel DBIC, the input channel is overwritten with calibrated displacement values.

If not specified, a new 32R raster layer is created.

If specified, the channel must already exist.

Ranges of channels or segments can be specified with negative values. For example, {1,-4,10} is internally expanded to {1,2,3,4,10}. When you are not specifying a range in this way, only 48 numbers can be specified explicitly.

FILREF

This parameter specifies the name of the input file containing the Delaunay segment.

MFILE

The name of a folder or text file containing the GNSS text files to be processed. For more information regarding MFILE usage, including the requirements for a valid file, see Using an MFILE with a CATALYST Professional algorithm.

Each input GNSS text file contains date indexed observations at a GNSS station. Each record has five fields:

date: YYYY-MM-DD.
latitude [degrees]: the WGS84 latitude in range [-90, 90).
longitude [degrees]: the WGS84 longtitude in range [-180, 180).
height [meters]: the height on the WGS84 ellipsoid.
deltaH [meters]: the cumulative height displacement.

CALWIN

The size of the image window, in pixels and lines, centered on each calibration point. In the window, all valid displacements are averaged, and the resulting value is used to obtain the correction associated with the given calibration point. The values of 1, 1, means that the exact value is used as the correction at each calibration point.

To define a square window, enter a single value, To define a rectangular window, enter two values. The window has the same size at all calibration points, based on the specified value or values.

If this parameter is not specified, the window will cover an area of 1000m x 1000m based upon the image sample sizes extracted from the metadata.

ADJMETHOD

The adjustment algorithm to use, which you can specify as an option.

The available options are as follows:

AVERAGE: Apply an average correction of calibration points (default).
MEDIAN: Apply the median correction of calibration points.
PLANE: Fit a plane to calibration points. The calibration points should be well distributed throughout the image when using this option.

MONITOR

The program progress can be monitored by printing the percentage of processing completed. A system parameter, MONITOR, controls this activity.

Available options are:

ON: Turns the monitor ON (default)
OFF: Turns the monitor OFF (recommended if running in batch or background mode)

Details

INSCALDEFO2 adjusts (raises or lowers) a raster of terrain-displacement values to GNSS points each stored in a text file. Each point represents a ground station whose movements are monitored by GNSS receivers at the time interval between the acquisition of the two SAR images used to derive the interferogram.

Typically, the displacement raster is produced by the INSPSN algorithm during the unwrapping of the SAR interferogram in deformation mode. Calibrating the raster of terrain deformation with GNSS points allows temporal analysis of several interferograms. Depending on the options you specify, the raster can be adjusted to:

Fit each calibration point, exactly
Match points within certain parameters, closely
Remove a single systematic movement by using an average of the differences

INSCALDEFO2 supports displacement rasters that are in the raw slant-range geometry. The slant-range rasters are identified automatically by the presence of the binary math model in input displacement file.

The specified text file contains the calibration GNSS points. The text file provides geodetic coordinates of points. The GNSS points will be reprojected to match the projection of the raster. If INSCALDEFO2 cannot project between the GNSS and the raster coordinate systems, processing will stop. INSCALDEFO2 uses three-dimensional transformation between the GNSS point and raster coordinate systems.

Each point outside the raster area or in a NoData area is skipped and counted as "outside file". Pixel values at the corresponding raster locations are corrected to adjust their displacements to GNSS observations.

If you specify a calibration window, and the number of lines and pixels in the window is greater than one, then all valid displacement values in the window are averaged, and the resulting value is used to derive the correction at the pixel. Any NoData values in the calibration window are ignored. If the window extends beyond the image, it is truncated to be fully within the image. The averaging of displacements compensates for possible misregistration of the two images forming the interferogram, and also derives a more stable correction for larger or distributed targets.

The corrections interpolate a 'difference surface' over the entire displacement raster, regardless of how far apart the points are. For example, with a single point, the entire raster is raised or lowered by the correction at this point. This can be a dangerous operation if a point is over an error in the displacement raster. You can prevent this by limiting the amount of adjustment by using the following options specified by ADJMETHOD:

AVERAGE: Apply an average correction of calibration points (default).
MEDIAN: Apply the median correction of calibration points.
PLANE: Fit a plane to calibration points. The calibration points should be well distributed throughout the image when using this option.

Example

In the following example, a SAR interferogram has been unwrapped by INSPSN. The interferogram has a 32R channel 2 with terrain displacements in meters. A new 32R channel 3 will be added to the raster file. A number of GNSS points are available in files GNSSPoints.txt.

The goal is to adjust the displacement raster by using the GNSS points to ensure that all residual errors, such as atmospheric effects, are removed. Based on the premise that random errors in the displacement raster are inevitable, a small calibration window is used, and the adjustment method is specified as PLANE. The raster is in the slant-range geometry and has a math model.

EASI>file    =   "UnwrappedDefo.pix" ! displacement raster to adjust
EASI>dbic    =   2                   ! raster displacement channel
EASI>dboc    =                       ! write the adjusted displacements to new channel
EASI>fileref =   "Delaunay.pix"      ! Delaunay triangulation
EASI>mfile   =   "mfile.txt"         ! input calibration points
EASI>calwin  =   3, 3                ! average nine pixels around every point
EASI>adjmethod = "PLANE"             ! fit plane using all points

EASI>run inscaldefo2

Environments	PYTHON :: EASI
Quick links	Description :: Parameters :: Parameter descriptions :: Details :: Example :: Related