The message transmitted form the GBAS ground facility to the aircraft contains one or more data sets that contain Final Approach Segment (FAS) data.

Each data set is transmitted with the associated vertical/lateral alert limits:

• FAS, MA Vertical Alert Limit (FASVAL)

• FAS, MA Lateral Alert Limit (FASLAL)

Each Final Approach Segment (FAS) data block contains the parameters that define a single precision approach.
It is self-contained and includes a means to preserve integrity from the time it is generated and validated to the time that it is used in airborne equipment.
All of the information necessary to describe the paths and its designation is contained within it.

This primarily includes the following:

• Airport identification

• Runway designation and position

• Procedure type (provides flexibility for advanced procedures such as departure or curved approach)

• Procedure name

• Runway surveyed points defining the FAS path.

The FAS path is a line in space defined by the following parameters:

• Landing Threshold Point or Fictitious Threshold Point (LTP/FTP)

• Flight Path Alignment Point (FPAP)

• LTP/FTP height

• Threshold Crossing Height (TCH)

• Glide Path Angle (GPA)