Working with synthetic-aperture radar imagery

In Object Analyst, the workflow of working with synthetic-aperture radar (SAR) data differs from that of other types of remote-sensing (RS) data.

You can process SAR data in its raw vendor format or, alternatively, you can ingest it to a PCIDSK (.pix) file for processing.

SAR imagery comes in many formats and processing levels. The specific SAR-data type and its processing level are identifiable by the matrix type in the image metadata. The matrix type determines which, if any, SAR preprocessing parameters you can apply, and which SAR attributes you can calculate, as shown in the following table.

Table 1. SAR matrix and channel types, segmentation processing, and predefined attribute types to calculate
Matrix type	Channel type**	Segmentation, preprocessing	Attribute types to calculate
[c1r] Single polarization, detected	1 x [16U] (uncalibrated) - or - 1 x [32R] (calibrated)	• Filtering • Tail trimming	• Statistical • Geometrical • Texture
[c1c] Single polarization, complex	1 x [C16S] (uncalibrated) - or - 1 x [C32R] (calibrated)	• Filtering • Tail trimming	• Statistical • Geometrical • Texture
[c2r] Dual polarization, detected	2 x [16U] (uncalibrated) - or - 2 x [32R] (calibrated)	• Filtering • Tail trimming	• Statistical • Geometrical • Texture
[s2c] Dual polarization, complex*	2 x [C16S] (uncalibrated) - or - 2 x [C32R] (calibrated)	• Filtering • Tail trimming	• Statistical • Geometrical • Texture
[s4c] Fully polarimetric, complex	4 x [C16S] (uncalibrated) - or - 4 x [C32R] (calibrated)	• Filtering • Tail trimming • Extra segmentation layers: - L1 (λ1) - L2 (λ2) - L3 (λ3)	• Statistical • Geometrical • Texture • Polarimetric

* Compact-polarimetric data is a special case of [s2c] data.
** Calibrated data is recommended.

Viewing the matrix type

You can determine the matrix type by viewing the metadata of the image in Focus.

To view the matrix type

In Focus, open the image.
On the Files tab, right-click the image for which you want to view the matrix type, and then click Properties.
The File Properties window appears.
On the MetaData tab, observe the entry in the table beside Matrix_Type.

With a given image, you can run segmentation on all channels or a subset thereof.

Note: Preprocessed or modified SAR images containing a mix of detected and complex channels cannot be segmented into objects.

With fully polarimetric complex data [s4c], the following additional layers are available for segmentation:

L1 (λ1)
L2 (λ2)
L3 (λ3)

The preceding layers correspond to the three eigenvalues of the covariance matrix of each image and can enhance land-cover attributes that are not always distinguishable from the original HH, HV, VH, and VV channels.

For typical workflow scenarios of procsessing SAR data in Object Analyst, see: