Compute Coherence (Image Analyst)

Available with Image Analyst license.

Summary

Computes the similarity between the reference and secondary input complex radar data.

The output is a coherence raster with a value range of 0 to 1 in which 0 indicates no coherence and 1 indicates perfect coherence. A value of 0.3 or above is considered a good coherence value.

Usage

  • The inputs must be a pair of coregistered complex radar datasets.

  • The output coherence raster can be used for coherent change detection. The output coherence raster can be used in InSAR and DInSAR workflows to assess the reliability of the interferogram pixels.

    For InSAR and DInSAR applications, the input radar data must have the same satellite geometry.

  • In the Geoprocessing pane, the Range Window Size and Azimuth Window Size parameters include information about the estimate size required to create an approximate square pixel for the Input Radar Data parameter value.

Parameters

LabelExplanationData Type
Input Reference Radar Data

The input reference complex radar data.

Raster Dataset; Raster Layer
Input Secondary Radar Data

The input secondary complex radar data.

Raster Dataset; Raster Layer
Output Radar Data

The output coherence radar data.

Raster Dataset
Polarization Bands
(Optional)

The polarization bands that will be corrected.

The first band is selected by default.

String
Range Window Size
(Optional)

The range window size in pixels.

The default value is 10.

Long
Azimuth Window Size
(Optional)

The azimuth window size in pixels.

The default value is the minimum number of pixels required to create an approximate square window. For example, if the Range Window Size parameter value is 10, the default will be 3.

Long

ComputeCoherence(in_reference_radar_data, in_secondary_radar_data, out_radar_data, {polarization_bands}, {range_window_size}, {azimuth_window_size})
NameExplanationData Type
in_reference_radar_data

The input reference complex radar data.

Raster Dataset; Raster Layer
in_secondary_radar_data

The input secondary complex radar data.

Raster Dataset; Raster Layer
out_radar_data

The output coherence radar data.

Raster Dataset
polarization_bands
[polarization_bands,...]
(Optional)

The polarization bands that will be corrected.

The first band is selected by default.

String
range_window_size
(Optional)

The range window size in pixels.

The default value is 10.

Long
azimuth_window_size
(Optional)

The azimuth window size in pixels.

The default value is the minimum number of pixels required to create an approximate square window. For example, if the range_window_size parameter value is 10, the default will be 3.

Long

Code sample

ComputeCoherence example 1 (Python window)

This example computes the similarity between the reference and secondary SAR images using a range and azimuth window size of 10 pixels.

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

outRadar = arcpy.ia.ComputeCoherence("Reference_SAR.crf",
    "Secondary_SAR_Coreg.crf", "VV", 10, 10) 
outRadar.save("Reference_Secondary_SAR_Coh.crf")
ComputeCoherence example 2 (stand-alone script)

This example computes the similarity between the reference and secondary SAR images using a range and azimuth window size of 10 pixels.

# Import system modules and check out ArcGIS Image Analyst extension license
import arcpy
arcpy.CheckOutExtension("ImageAnalyst")
from arcpy.ia import *

# Set local variables 
in_reference_radar_data = r"C:\SAR\Reference_SAR.crf" 
in_secondary_radar_data = r"C:\SAR\Secondary_SAR_Coreg.crf" 
polarization_bands ="VV" 
range_window_size = 10 
azimuth_window_size=10 

# Execute  
outRadar = arcpy.ia.ComputeCoherence(in_reference_radar_data, 
    in_secondary_radar_data, polarization_bands, range_window_size, 
    azimuth_window_size)  
outRadar.save(r"C:\SAR\Reference_Secondary_SAR_Coh.crf")

Licensing information

  • Basic: Requires Image Analyst
  • Standard: Requires Image Analyst
  • Advanced: Requires Image Analyst

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