AIRSAR -- AIRSAR Polarimetric Format

Most variants of the AIRSAR Polarimetric Format produced by the AIRSAR Integrated Processor are supported for reading by GDAL. AIRSAR products normally include various associated data files, but only the imagery data themselves is supported. Normally these are named mission_l.dat (L-Band) or mission_c.dat (C-Band).

AIRSAR format contains a polarimetric image in compressed stokes matrix form. Internally GDAL decompresses the data into a stokes matrix, and then converts that form into a covariance matrix. The returned six bands are the six values needed to define the 3x3 Hermitian covariance matrix. The convention used to represent the covariance matrix in terms of the scattering matrix elements HH, HV (=VH), and VV is indicated below. Note that the non-diagonal elements of the matrix are complex values, while the diagonal values are real (though represented as complex bands).

Band 1: Covariance_11 (Float32) = HH*conj(HH)
Band 2: Covariance_12 (CFloat32) = sqrt(2)*HH*conj(HV)
Band 3: Covariance_13 (CFloat32) = HH*conj(VV)
Band 4: Covariance_22 (Float32) = 2*HV*conj(HV)
Band 5: Covariance_23 (CFloat32) = sqrt(2)*HV*conj(VV)
Band 6: Covariance_33 (Float32) = VV*conj(VV)

The identities of the bands are also reflected in metadata and in the band descriptions.

The AIRSAR product format includes (potentially) several headers of information. This information is captured and represented as metadata on the file as a whole. Information items from the main header are prefixed with "MH_", items from the parameter header are prefixed with "PH_" and information from the calibration header are prefixed with "CH_". The metadata item names are derived automatically from the names of the fields within the header itself.

No effort is made to read files associated with the AIRSAR product such as mission_l.mocomp, mission_meta.airsar or mission_meta.podaac.