Polarimetric Parameters module

Name	Caption
Input Scenes	Input scenes
Output Folder	Output folder
Overwrite Results	Overwrite existing results
Send Email	Email notification settings
Filter When Necessary	Filter scenes when required
Filter Type	Filter type
Filter Size	Filter size (pixels)
Number of Looks	Number of looks
Total Power	Total power (span) intensity
HH Intensity	HH intensity
HV Intensity	HV intensity
VH Intensity	VH intensity
VV Intensity	VV intensity
Intensity Ratios	Intensity ratios to calculate
Scaling Type	Scaling type
Phase Differences	Phase differences to calculate
Angular Units	Angular units
Touzi Decomposition	Generate Touzi decomposition
Angular Units	Angular units
Freeman-Durden Decomposition	Generate Freeman-Durden decompositions
Cloude-Pottier (H/a) Decomposition	Generate Cloude-Pottier (H/a) decompositions
Polarimetric Discriminators	Generate polarimetric discriminators
Orientation Step Size	Orientation angle step size (degrees)
Ellipticity Step Size	Ellipticity angle step size (degrees)
Touzi Discriminators	Generate Touzi discriminators
Ortho Input Scenes	Orthorectify input scenes
DEM Source	DEM tile source
Output File Type	Output file type
Output File Options	Output file options
Output Map Units	Output projection
Output Pixel Size	Output pixel size
Resampling Method	Resampling method

Parameter descriptions

Input Scenes

The input scenes from which to create polarimetric parameters.

Output Folder

The path and name of the folder to which to write the output files.

Overwrite Results

Select this check box to overwrite the existing output files, if any exist. If this check box is left clear, and an output file exists in the relevant folder, the status of the job displays a message informing you of the existence and name of the output file. The message is also written to the event log of the job.

Send Email

If necessary, you can set up CATALYST Enterprise to send an email notification on job start and job completion.

With this check box selected, an email message is sent to each address specified in the Email Addresses box after the job starts and on completion.

You can specify one or more addresses, and each must be separated by a comma or a semi-colon. The email address of the user currently logged in displays by default.

Filter When Necessary

Select whether to apply a filter to scenes when spatial filtering (multilooking) is required. If selected, the module applies the filter specified by the Filter Type parameter before performing other functions.

Filter Type

The type of filter to apply to the ingested data.

Available options are:

Adaptive Lee: applies a Lee adaptive filter to a SAR data set. It reduces speckle in the image, while preserving the edges. Edges are preserved by using an edge detector to filter only homogeneous neighborhoods.
Boxcar: applies a boxcar filter to a SAR data set and is used commonly to increase the effective number of looks (ENL) in single-look or multi-look SAR data. This filter reduces the speckle inherent to SAR images by local block-averaging.

This parameter is mandatory when the Apply Filter check box is selected.

Filter Size

The filter size in horizontal (columns) and vertical (lines) directions, in pixels. The value must be an odd integer between 1 and 33.

When Adaptive Lee is selected for the Filter Type parameter, the window must be specified as a square for the Filter Size parameter, such as 9 x 9 pixels (9,9). When available, the Boxcar filter type can be specified as a rectangle, such as 5 x 9 pixels (5,9).

If no value is specified for this parameter, the module uses a default filter of 7 x 7 pixels (7,7).

Number of Looks

The equivalent number of looks (ENL) in the input data set. The minimum valid value is 1 and the maximum is 50.

A float greater than or equal to one should be specified only when the data has already been speckle-filtered. The maximum value depends on the type of product being used. If no value is specified for this parameter, a default value of 1, which corresponds to single-look images, is applied.

Note: You can estimate the ENL by calculating the mean-squared-to-variance ratio (of the intensity data) in a homogenous area.

This parameter applies only when the Adaptive Lee filter is selected for the Filter Type parameter.

Total Power

Select whether to generate total power.

HH Intensity

Select this check box to generate HH intensity.

HV Intensity

Select this check box to generate HV intensity.

VH Intensity

Select this check box to generate VH intensity.

VV Intensity

Select this check box to generate VV intensity.

Intensity Ratios

The intensity ratios to calculate; for example, HH/VV, VV/HH, and other intensity ratios.

Scaling Type

Available options are:

Decibel
Linear

When an input scene contains more than one image channel; that is, quad-pol, dual-pol or compact-pol data), the total power is calculated automatically from all available channels.

Phase Differences

Lists the phase differences to calculate; for example, HH-VV, VV-HH, RR-LL, and so on.

Angular Units

The angular units to use for Touzi parameters.

Available options are:

Radian (default)
Degree

Touzi Decomposition

Select this check box to generate a Touzi decomposition.

When you select this check box, the module performs an incoherent target scattering decomposition in terms of roll invariant parameters for a fully polarimetric SAR (POLSAR) data set. It creates an image of 15 decomposition parameters. For each of the primary, secondary, and tertiary eigen vectors, the orientation angle (psi), dominant eigenvalue (lambda), Touzi alpha_s angle, Touzi phase, and helicity(tau) are computed.

Scattering type angles (alphas-1, alphas-2, alphas-3): along with phi, represents the polar coordinates of the symmetric scattering type
Touzi phase (phis-1, phis-2, phis-3): along with alphas, represents the polar coordinates of the symmetric scattering type
Target orientation angles (psi-1, psi-2, psi-3): represents the orientation (tilt) angle required to maximize the polarization
Helicity (tau-1, tau-2, tau-3): measure of target symmetry
Eigenvalues (lambda-1, lambda-2 and lambda-3): represents the intensity of the scattering

The dominant, secondary, and tertiary parameters uniquely characterize the properties, type, and proportions of the partially coherent scattering mechanisms. The dominant scattering types (alphas-1, phis-1, psi-1, tau-1 and Lambda-1) are usually sufficient to get a good understanding of the scattering properties of targets. This information can also aid in image classification or interpretation.

The dominant (main scattering) parameters are written to the first five channels. The secondary scattering parameters are written to the next five channels, and the tertiary scattering parameters to the last five channels. The dominant, secondary, and tertiary parameters uniquely characterize the properties, type, and proportions of the partially coherent scattering mechanisms. This information can be used further for image classification or interpretation.

Angular Units

From the list, select the angular units to use for the Touzi decomposition.

Available options are:

Radian (default)
Degree

Freeman-Durden Decomposition

Select this check box to generate Freeman-Durden decompositions.

When you select this check box, the module performs an unsupervised Freeman-Durden decomposition of a fully polarimetric SAR (POLSAR) data set. It partitions the total power at every image pixel into contributions from three scattering mechanisms: double-bounce (such as urban features), volume scattering (such as vegetation canopy), and rough surface (such as water).

Cloude-Pottier (H/a) Decomposition

Select this check box to create an image of four parameters for a fully polarimetric SAR (POLSAR) data set:

Entropy (Η)
Alpha angle (α)
Beta angle (β)
Anisotropy (Α)

These parameters characterize the properties of partially coherent scattering by computing the proportion and type of the scattering mechanism for all of the features in your image. You can also use this information for image classification. The eigenvalues and eigenvectors used to compute these parameters can also be output, if required.

The alpha angle (between 0 and 90 degrees) characterizes the scattering mechanism. For example, alpha=0 degrees indicates a trihedral scatterer or a smooth surface; alpha=45 degrees indicates a dipole scatterer (often assigned to volume structures); alpha=90 degrees indicates a dihedral scatterer (often related to double-bounce).

The beta angle (between 0 and 90 degrees) is twice the preferred orientation angle of the scatterer and, therefore, characterizes the dominant polarization.

The entropy measures the amount of mixing between the three scattering mechanisms, where values close to 0 indicate a single scattering mechanism, and values close to 1 indicate an equal mixture of three scattering mechanisms (equal eigenvalues).

The anisotropy characterizes the amount of mixing between the second and third scattering mechanism. The anisotropy A=0 indicates that the two mechanisms are mixed in equal proportions and that their eigenvalues are equal. An anisotropy value close to 1 indicates that the second mechanism dominates over the third mechanism and that the second eigenvalue is much larger than the third eigenvalue. The anisotropy is set to 0 when both eigenvalues are 0.

Polarimetric Discriminators

Select this check box to generate polarimetric discriminators.

When you select this check box, the module calculates a number of polarimetric discriminators for a fully polarimetric SAR (POLSAR) data set. Polarimetric discriminators are useful to characterize the features in your image by identifying the different types of scattering mechanism. The discriminators are based on the polarimetric synthesis, and describe the polarimetric response of features in the image.

The output channels contain the polarimetric discriminators stored in the following order (the intensity values are in linear scale):

Maximum degree of polarization
Minimum degree of polarization
Maximum intensity of the of the completely polarized component
Orientation angle (psi) at the maximum of the completely polarized component
Ellipticity angle (chi) at the maximum of the completely polarized component
Minimum intensity of the completely polarized component
Orientation angle (psi) at the minimum of the completely polarized component
Ellipticity angle (chi) at the minimum of the completely polarized component
Maximum intensity of the completely unpolarized component
Minimum intensity of the completely unpolarized component
Maximum of the received power
Minimum of the received power
Maximum of the scattered intensity
Minimum of the scattered intensity
Coefficient of variation
Fractional polarization

Orientation Step Size

The step, in degrees, for the orientation (psi) angle used in the search for the minimum and maximum of the polarization response. The value you specify must be between 1 and 90; the default is 10.

This parameter is optional.

Ellipticity Step Size

The step, in degrees, for the ellipticity (chi) angle that is used in the search for the minimum and maximum of the polarization response. The value you specify must be between 1 and 45; the default is 10.

This parameter is optional.

Touzi Discriminators

Select this check box to generate Touzi discriminators.

When you select this check box, the module computes polarimetric discriminators from a fully polarimetric SAR (POLSAR) data set. The computed discriminators include the Touzi anisotropy, the degrees of minimum and maximum polarization response, and the difference between the maximum and minimum response.

Ortho Input Scenes

Select this check box to orthorectify the input raw SAR imagery.

With this check box selected, the module orthorectifies the input scenes based on the value selected for the Resampling Method parameter.

DEM Source

The name of a single digital elevation model (DEM) file or a folder containing one or more DEM tiles.

This parameter can be specified by using any of the following:

Name of a single DEM file; for example, C:\data\DEM\dem.pix
Name of a folder containing one or more DEM tiles and an associated index.txt file; for example, C:\data\DEM
Name of an index file; for example, C:\data\DEM\index.txt

The index.txt file lists the DEM files contained in the specified folder and provides information describing each DEM tile. The information in the DEM index file supersedes other DEM parameters in the module; all other DEM-related parameters are ignored. For more information about the format of the index.txt file and specific requirements for the individual DEM tiles, see Format of the DEM index file.

When the value of DEM Source is the name of an existing folder, the module searches that folder for a file named index.txt, and a set of DEM raster tiles. The index.txt file contains a single vector channel that lists the DEM files contained in the specified folder and provides information describing each DEM tile.

If no value is specified for this parameter, the module uses the default global DEM installed with CATALYST Enterprise (gmted2010).

Output File Type

The format of the output file.

For more information on the supported file formats, see GDB-supported file formats.

Output File Options

The options to apply when creating the output file or files. The available options are specific to the file format; in each case, the default of no options is allowed.

For more information on the options available for the output file type you specify, see GDB-supported file formats.

Output Map Units

The projection of the output imagery.

The value of this parameter must be in the PCI Projection String format.

The standard definitions are:

PIXEL: Pixel and line (not for use with DEM extraction)
UTM: Universal Transverse Mercator

The value specified can be the UTM grid zone number and row, and Earth model, as follows:
```
UTM [mm] [r] [Ennn]
```
where:
- [mm] is the two-digit zone number between 1 and 60
- [r] is the zone row: a single letter between N and X for north of the equator and between C and M for south of the equator. Zone rows A, B, Y, and Z are not supported; rows I and O do not exist.
- [Ennn] specifies the Earth model, where the model number is between 0 and 19. If the Earth model is not specified, it is assumed to be E000 (Clarke 1866).
SPCS: State Plane Coordinate System

The SPCS zone number and Earth model can be specified as follows:
```
SPCS [mmmm] [Ennn]
```
where:
- [mmmm] is the four-digit zone number
- [Ennn] specifies the Earth model, where the model number is between 0 and 19. If the Earth model is not specified, it is assumed to be E000 (Clarke 1866).
LONG/LAT: Longitude and latitude

The Earth model can be specified for LONG/LAT (and other units except PIXEL), as follows:
```
LONG/LAT [Ennn]
```
If the Earth model is not specified, it is assumed to be E000 (Clarke 1866).
EPSG: European Petroleum Survey Group code

You can specify the projection by entering an EPSG code defined by the Open Geospatial Consortium (OGC). For information on the code definitions, visit epsg.org and spatialreference.org.

The EPSG code is specified using the EPSG keyword followed by an integer and separated by a colon; for example:
```
EPSG:4326
```
Most common EPSG codes are supported.
METER: Image along-row and along-column meters
FEET: Image along-row and along-column feet
You can also specify the label of a projection you define, if the projection exists in the userproj.txt file; otherwise, you must enter the projection-parameter information as a string separated by the vertical bar (|). The projection-parameter string defines 18 parameters delimited by spaces, including the following:
- Dearth
- RefLong
- RefLat
- StdParallel1
- StdParallel2
- FalseEasting
- FalseNorthing
- Scale
- Height
- Long1
- Lat1
- Long2
- Lat2
- Azimuth
- LandsatNum
- LandsatPath
- UnitsCode
For example, the projection named 'France93' can be specified, as follows:
```
LCC D350 | 0 0 3.0 46.5 44.0 49.0 700000 6600000 0 0 0 0 0 0 0 0 0 -1
```

If you do not specify a value for Output Map Units, the map unit of the input image is used for the output image. If the input data is a variety of map units, the map unit of each output image is that of its corresponding input image. In such a case, it is recommended that you specify the output map units.

You can also specify the label of a projection defined in the userproj.txt file.

Output Pixel Size

The sample size of the output imagery.

The output pixel size must be specified in the value (units) of Output Map Units; for example, when the value of Output Map Units is specified as a UTM zone, the pixel output size must be in meters. When the value is specified as Long/Lat, the pixel size must be in decimal degrees.

If a single value is specified, that value applies to both x and y values.

If no value is specified for this parameter, the pixel output size is based on the input math model associated with each scene in the input folder.

Resampling Method

The resampling method to use during processing.

Available resampling options are:

Cubic: cubic convolution. This method determines the gray level from the weighted average of the 16 pixels closest to the specified input coordinates and assigns that value to the output coordinates. The resulting image is slightly sharper than one produced by bilinear interpolation, and it does not have the disjointed appearance produced by nearest-neighbor interpolation. This is the default value.
Nearest Neighbor: nearest-neighbor interpolation. This method identifies the gray level of the pixel closest to the specified input coordinates and assigns that value to the output coordinates. Although this method is the most efficient in computation time, it introduces small offsets in the output image. The output image may be offset spatially by up to half a pixel, which may cause the image to have a jagged appearance.
Bilinear: bilinear interpolation. This method determines the gray level from the weighted average of the four closest pixels to the specified input coordinates and assigns that value to the output coordinates. An image with a smoother appearance than nearest-neighbor interpolation is created, but the gray-level values are altered in the process, resulting in blurring or degraded image resolution.
Lagrange-4: four-point Lagrange interpolation
Lagrange-8: eight-point Lagrange interpolation
Sinc-8: eight-point sin(x)/x
Sinc-16: 16-point sin(x)/x
Average: Average resampler for creating downsampled products
Gaussian: Gaussian resampler
Median: Median resampler for creating downsampled products

Polarimetric Parameters module

Description

Parameters

Parameter descriptions

Details

References