AIM

4/3/14

1−1−37

Navigation Aids

relative to the approach; therefore, aircrews must not

use the TLS signal for navigation unless they have

received approach clearance and completed the

required coordination with the TLS ground equip-

ment operator. Navigation fixes based on

conventional NAVAIDs or GPS are provided in the

special instrument approach procedure to allow

aircrews to verify the TLS guidance.

d. Special Category I Differential GPS (SCAT

−

I DGPS)

1.

The SCAT−I DGPS is designed to provide

approach guidance by broadcasting differential

correction to GPS.

2.

SCAT−I DGPS procedures require aircraft

equipment and pilot training.

3.

Ground equipment consists of GPS receivers

and a VHF digital radio transmitter. The SCAT−I

DGPS detects the position of GPS satellites relative

to GPS receiver equipment and broadcasts differen-

tial corrections over the VHF digital radio.

4.

Category I Ground Based Augmentation

System (GBAS) will displace SCAT−I DGPS as the

public use service.

REFERENCE

−

AIM, Para 5

−4−7f, Instrument Approach Procedures.