Details
Many SAR images are delivered in single-look (SLC) or multilook (MLC) complex format. PSIQINTERP provides the ability to manipulate complex-valued layers.
- 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), Output data interpretation 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, Output data interpretation 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 (
) to real-valued layers, where r corresponds to the magnitude and 
to the (unwrapped) phase, in degrees, Output data interpretation 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 () = (5.71684, 47.98211), Output data interpretation 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 Output data interpretation is Complex, and as when Output data interpretation 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 Output data interpretation 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 Output data interpretation 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 Output data interpretation as Complex, the first channel is converted from 2.4 dB = 100.24 = 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.