GBAS/SCAT-I Mode (Options R&S
EVSG-K4/-K5)
R&S
®
EVSG1000
124
User Manual 1178.6227.02 ─ 04
The GBAS specification [1] defines the TDMA timing structure, including timing budget
of the VDB bursts, burst data contents and message encoding in great details. The
R&S
EVSG1000 receives the required training sequence, decodes the message
according to [1] and demodulates the D8PSK modulated data automatically.
7.1.3
Final Approach Segment (FAS) Construction Data
According to the standard [1], the message type 4 contains one or more data sets that
contain approach data, associated vertical/lateral alert limits, and/or the Terminal Area
Path (TAP).
The FAS path is a line in space that defines the path an airplane follows on its final
approach. This line is defined by the Landing Threshold Point/Fictitious Threshold
Point (LTP/FTP), Flight Path Alignment Point (FPAP), Threshold Crossing Height
(TCH), and the Glide Path Angle (GPA).
Figure 7-3: Final Approach Segment (FAS) diagram, according to [1]
LTP/FTP = Landing Threshold Point/Fictitious Threshold Point; point at the center of the landing runway,
defined by its WGS84 coordinates
GPIP
= Glide Path Intercept Point; the point where the final approach path intercepts the local level plane
FPAP
= Flight Path Alignment Point; point at the end of the runway that in conjunction with the LTP/FTP
defines the geodesic plane of the precision final approach, landing and flight path.
TCH
= Threshold Crossing Height
GPA
= Glide Path Angle; angle at the TCH that describes the intended angle of descent at the final
approach path.
The coordinates of the LTP/FTP are defined in WGS84 coordinates. In this coordinate
system, a location is identified by three coordinates, the altitude, the latitude and the
longitude.
Basics on GBAS and SCAT-I Analysis
