8. CNS/ATM

Question 1

INMARSAT services

(4)

Answer 1

INMATSATs services include

• communications for ATC
• aeronautical ops control
• aeronautical public services
• ATS Datalink

Question 2

MTSAT provided

• SBAS (satellite based augmentation system) for improved accuracy and reliability of GPS navigation;
• CPDLC (controller pilot data link communications
• ADS (automatic dependent surveillance) for oceanic flights

SBAS function is now being transferred to QZSS (Quasi Zenith Satellite System)

Question 3

INMARSAT voice communication quality vs HF

Answer 3

The quality and coverage of communications by INMARSAT is much better than the HF voice communication, except in the polar regions

Question 4

Levels of GPS data accuracy

Answer 4

There are two levels of GPS data accuracy,

• Coarse Acquisition (C/A) code and
• precision (P/Y) code.

C/A code is applied to airline operations.

Question 5

DGPS

Answer 5

Differential GPS (DGPS) is a ground facility that uses a GPS receiver with a highly accurate clock.

DGPS detects errors in computed position and provides other GPS receivers in the area with position correction data.

DGPS is a form of GBAS (Ground Based Augmentstion System).