Structure of the Second Protected Data Field (PDF-2)

The PDF-2 is available only in the long message format. It is comprised of the twenty-six bits (bits 107 to 132) following the BCH-1.

The second protected data field (PDF-2) is used for encoding supplementary data and position data as defined for the various location protocols. However, administrations can also define their own bit assignments for this field to satisfy specific national requirements, as provided for in the national user protocol.

The terminology used in Cospas-Sarsat to define the second protected field (SPF), the second protected data field (PDF-2) and second BCH error correcting field (BCH-2) is illustrated below.