Unwrap Phase (Image Analyst Tools)

Summary

Removes the phase ambiguities and solves for continuous phase values for single look complex (SLC) data.

Usage

The phase values in an interferogram are wrapped within a limited range, from -π to π, which makes it difficult to interpret deformation or heights. Unwrapping the phase removes the phase ambiguities and obtains continuous phase values.
To optimize unwrapping, the tool computes effective coherence, which is the phase variance of the input radar data. Phase variance is a type of coherence measurement that uses phase values to determine the reliability of an interferogram pixel.

High variance indicates low effective coherence and a nonreliable pixel.

Low variance indicates high effective coherence and a reliable pixel.

The computed effective coherence is used to mask areas of low coherence, below the effective coherence threshold parameter value.
The output of this tool will be displayed using the Bathymetric Scale color scheme.

Label	Explanation	Data type
Input Radar Data	The input complex wrapped interferogram.	Raster Dataset; Raster Layer
Output Radar Data	The phase of the unwrapped interferogram.	Raster Dataset
Polarization Bands (Optional)	The polarization bands that will be corrected. The first band is selected by default.	String
Unwrap Phase Method (Optional)	Specifies the unwrapping method that will be applied. Least squares PCG—The least squares Preconditioned Conjugate Gradient (PCG) method will be used. This method uses a linear system of equations to iteratively solve for the optimal unwrapped phase solution. This is the default.	String
Effective Coherence Threshold (Optional)	The effective coherence threshold that will be used for masking. The default value is 0.3.	Double

UnwrapPhase(in_radar_data, out_radar_data, {polarization_bands}, {unwrap_phase_method}, {effective_coherence_threshold})

Name	Explanation	Data type
in_radar_data	The input complex wrapped interferogram.	Raster Dataset; Raster Layer
out_radar_data	The phase of the unwrapped interferogram.	Raster Dataset
polarization_bands [polarization_bands,...] (Optional)	The polarization bands that will be corrected. The first band is selected by default.	String
unwrap_phase_method (Optional)	Specifies the unwrapping method that will be applied. `LEAST_SQUARES_PCG`—The least squares Preconditioned Conjugate Gradient (PCG) method will be used. This method uses a linear system of equations to iteratively solve for the optimal unwrapped phase solution. This is the default.	String
effective_coherence_threshold (Optional)	The effective coherence threshold that will be used for masking. The default value is 0.3.	Double

Code sample

UnwrapPhase example 1 (Python window)

This example demonstrates splitting the phases using the least squares PCG method.

import arcpy
arcpy.env.workspace = r"C:\Data\SAR"

outRadar = arcpy.ia.UnwrapPhase("Igram_Dbst_ML_Topo_Filt.crf", "VV", "PCG", 0.4)
outRadar.save("Igram_Dbst_ML_Topo_Filt_Unw.crf")

UnwrapPhase example 2 (stand-alone script)

This example demonstrates splitting the phases using the least squares PCG method.

# Import system modules
import arcpy
from arcpy.ia import *

# Set local variables
in_radar=r"C:\SAR\Igram_Dbst_ML_Topo_Filt.crf"
out_radar=r"C:\SAR\Igram_Dbst_ML_Topo_Filt_Unw.crf"
polarization="VV"
unwrap_method="LEAST_SQUARES_PCG"
coherence_thresh=0.4

outRadar = arcpy.ia.UnwrapPhase(in_radar, polarization, unwrap_method, coherence_thresh)
outRadar.save(out_radar)

Environments

Cell Alignment, Cell Size, Compression, Current Workspace, Extent, Geographic Transformations, NoData, Output CONFIG Keyword, Output Coordinate System, Parallel Processing Factor, Pyramid, Raster Statistics, Resampling Method, Scratch Workspace, Snap Raster, Tile Size

Licensing information