PSIQINTERP

Description

PSIQINTERP converts back and forth between complex-valued layers and real-valued interpretations. For example, you can use the algorithm to do the following:

Convert synthetic-aperture radar (SAR) single-look complex (SLC) to detected values or to extract the phase of the complex data
Extract the real or imaginary parts of a complex number and store each part in a separate channel
Combine two real-valued layers into a single complex layer or convert between various complex representations

Parameters

psiqinterp(fili, dbic, cinterp, dboc, filo, ftype, foptions)

Name	Type	Caption	Length	Value range
FILI *	str	Input-file name	1 -
DBIC	List[int]	Database input-channel list	0 -
CINTERP *	str	Complex SAR interpretation	1 -	Intensity\|Amplitude\|Phase R\|Phase D\|Decibel\|Real\|Imaginary\|RI\|IQ\|Complex\|Polar
DBOC	List[int]	Database output-channel list	0 -
FILO *	str	Database output-file name	1 -
FTYPE	str	Output-file type	0 -	Default: PIX
FOPTIONS	str	Output-file options	0 -

* Required parameter

Parameter descriptions

FILI

The name of the input file that contains the complex or real-valued channel or channels to modify or interpret.

DBIC

The list of input image channels to convert.

To convert to intensity, amplitude, phase in radians, phase in degrees, decibels, real or imaginary part, or to convert between complex representations, the input layer must be of type [C16S] or [C32R].

To create complex-valued or polar-valued layers, the input must be real values [32R] or signed integer [16S] layers.

CINTERP

The interpretation type. You can enter either the short or long form of the following values:

Int or Intensity: Intensity
Amp or Amplitude: Amplitude
Rad or Phase R: Phase in radians
Deg or Phase D: Phase in degrees
dB or Decibel: Decibel
RE or Real: Real part of the complex number
IM or Imaginary: Imaginary part of the complex number
IQ or RI: Real and imaginary part of the complex number
Complex: Complex values in Cartesian format
Polar: Complex values in polar format

DBOC

If the output file (FILO) corresponds to a new file, do not specify a value for DBOC. If the output file exists already, the number of channels must equal that specified for the combined value of DBIC and CINTERP.

Note: If the value of CINTERP is IQ or RI, the number of channels must be twice that specified for DBIC.

If CINTERP is Complex or Polar, the number of real-valued input channels must be twice the number specified for DBIC. If the input and output are complex valued, the number of channels for DBIC and DBOC must be identical.

If the output file exists already, the channels specified for DBOC must be in either 32-bit real format [32R] for real-valued output or one of [C16R] (for signed complex integer) or [C32R] for (floating-point complex) valued output. If the file does not exist already, the default will be [32R] for real-valued output and [C32R] for complex-valued output.

FILO

The name of the output file to create.

The name can be that of either a new or an existing file, but must differ from that of the input file. If the file exists already, the size—that is, the number of image rows and columns—of the output file must match the size of the input file.

FTYPE

The format of the output file.

The format must be a GDB-recognized type.

The following formats are supported:

PIX: PCIDSK
RAW: Unprocessed, typically unformatted, data
TIF: Tagged Image File Format

The default value is PIX.

For a complete list of GDB-recognized file types, see GDB-supported file formats.

FOPTIONS

The options to apply when creating the output file specific to the file format, such as compression schemes, file-format subtypes, and so forth.

Typically, the available options for a format include a compression scheme, format subtype, or other information. In most applications, the default (no options) is suitable for most applications.

For a complete list of GDB-recognized file types and their available options, see GDB-supported file formats.

Details

Many SAR images are delivered in single-look (SLC) or multilook (MLC) complex format. PSIQINTERP provides the ability to manipulate complex-valued layers.

The algorithm can do the following:

Convert SAR single-look complex (SLC) to detected values or to extract the phase of the complex data
Extract the real or imaginary parts of a complex number and store each part in a separate channel
Combine two real-valued layers into a single complex layer or convert between various complex representations

When converting from a complex-valued layer written in Cartesian format (a + bi) to real-valued layers, where a corresponds to the real part (I) and b to the imaginary part (Q), CINTERP supports the following transformations:

Intensity: Corresponds to I² + Q².
Note: Intensity is also known as power.
Amplitude: Corresponds to the square root of the intensity: .
Phase in radians: Corresponds to arctan (Q ÷ I) in radians.
The output values range from - through .
Phase in degrees: Corresponds to arctan (Q ÷ I) in degrees.
The values range from -180 through 180.
Decibel: Corresponds to 10 × log10 (intensity) or, equivalently, to 20 × log10 (amplitude).
Real part: Corresponds to I only.
Imaginary part (only): Corresponds only to Q.
Real and imaginary: Corresponds to I and Q stored on two separate channels.

With the Cartesian complex number, (a + bi) = 0.206871 − 0.0338254i, CINTERP supports the following transformations:

Intensity: (0.206871)² + (-0.0338254)² = 0.0439399
Amplitude:
Phase in radians: arctan (−0.0338254 ÷ 0.206871) = −0.162075 radians
Phase in degrees: arctan (−0.0338254 ÷ 0.206871) = −9.28623 degrees
Decibel: 10 × log10 (0.0439399) = −13.571 dB or 20 × log10 (0.2096184) = −13.571 dB
Real part: 0.206871
Imaginary part: −0.0338254

When converting from a complex-valued layer in polar format ( rho, theta ) to real-valued layers, where r corresponds to the magnitude and theta to the (unwrapped) phase, in degrees, CINTERP supports the following transformations:

Intensity: Corresponds to r ²
Amplitude: Corresponds to r
Phase in radians: Corresponds to × ranging from - through
Phase in degrees: Corresponds to ranging from - through
Decibel: Corresponds to 10 × log10 (intensity) or, equivalently to 20 × log10 (amplitude)
Real part: Corresponds to r × cos
Imaginary part (only): Corresponds to r × sin
Real and imaginary part: Corresponds to I and Q stored on two separate channels

With the polar-complex number ( rho, theta ) = (5.71684, 47.98211), CINTERP supports the following transformations:

Intensity: (5.71684)² = 32.68226
Amplitude: 5.71684
Phase in radians: (47.98211 × ) = 0.83745
Phase in degrees: 47.98211
Decibel: 10 × log10 (32.68226) = 15.143 dB or 20 × log10 (5.71684) = 15.143 dB
Real part: 5.71684 × cos (47.98211°) = 3.82664
Imaginary part: 5.71684 × sin (47.98211°) = 4.24725

To convert from real values to complex layers, the input layers specified in the input-channel list must be real valued with two channels of input required for each complex-valued output channel. The real-valued input can be converted to complex layers in either Cartesian or polar format. The two real values a and b are interpreted as (a + bi) when CINTERP is Complex, and as rho, theta when CINTERP is Polar.

For example, if the input data specified in the input-channel list contains the value 2.4 in the first channel and -1.9 in the second, with CINTERP as Complex, the Cartesian pair is written as (2.4 -1.9i). The intensity is (2.4)² + (-1.9)² = 9.37 and phase of arctan (-1.9/2.4) = -38.367 degrees. If CINTERP is Polar, the intensity is (2.4)² = 5.76, and the phase is interpreted as -1.9 degrees.

The exception to this rule is when the real valued input layer has the Scale or SARPixelContent metadata tag. These metadata tags indicate the values are to be always interpreted as intensity, amplitude or decibel. If these metadata tags are present, the input is converted prior to being written as a complex pair.

For example, if the first layer of input data contains the Scale = decibel metadata tag with a value of 2.4, and the second channel has a value of -1.9, with CINTERP as Complex, the first channel is converted from 2.4 dB = 10^0.24 = 1.7378 prior to writing the output as the complex number (1.7378, -1.9).

PSIQINTERP accepts calibrated or noncalibrated 16-bit signed channels [C16S] in raw vendor format as input. With SAR data sets distributed in multiple files, use the key-file name. For more information, see GDB-supported file formats.

Example

In the following example, the four channels of a SLC RADARSAT-2 Fine QuadPol image are ingested with the sigma nought calibration applied. The four resulting complex channels [C32R] are then converted to intensities using PSIQINTERP. The resulting file will have four channels [32R].

from pci.saringest import saringest
from pci.psiqinterp import psiqinterp

fili = "product.xml"
filo = "RS2_FQ17_slc.pix"
dbiw = []
poption = "NEAR"
dblayout = "BAND"
calibtyp = "SIGMA"

saringest(fili, filo, dbiw, poption, dblayout, calibtyp)

fili = "RS2_FQ17_slc.pix" 
dbic = [1,2,3,4] 
cinterp = "Int" 
dboc = []
filo = "RS2_FQ17_int.pix" 
ftype = "PIX" 
foptions = "" 

psiqinterp(fili, dbic, cinterp, dboc, filo, ftype, foptions)

Environments	PYTHON :: EASI :: MODELER
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