Garmin MX20 - Manual (Page 56)


Detailed Operation
As TIS target location is determined by ground based radar, coverage, range and target positional accuracy are
highly dependent on relative location to the actual radar site.
Traffic Information Services-Broadcast (TIS-B) is the broadcast of traffic information to ADS-B equipped aircraft
from ADS-B ground stations. The source of this traffic information is derived from ground-based air traffic
surveillance sensors, typically radar. TIS-B is intended to provide ADS-B equipped aircraft with a more complete
traffic picture in situations where not all nearby aircraft are equipped with ADS-B. The advisory-only applica-
tion enhances a pilot’s visual acquisition of other traffic. TIS-B service is becoming available in selected locations
where there are both adequate surveillance coverage from ground sensors and adequate broadcast coverage from
Ground Based Transceivers (GBTs). The quality level of traffic information provided by TIS-B is dependent upon
the number and type of ground sensors available as TIS-B sources and the timeliness of the reported data.
In order to receive TIS-B services, the following conditions must exist:
1. The host aircraft must be equipped with a UAT ADS-B transmitter / receiver or transceiver, and a
Cockpit Display of Traffic Information (CDTI). As the ground system evolves, the ADS-B data link may
be either UAT or 1090 ES, or both.
2. The host aircraft must fly within the coverage volume of a compatible GBT that is configured for TIS-B up-
links. (Not all GBTs provide TIS-B due to a lack of radar coverage or because a radar feed is not available).
3. The target aircraft must be within the coverage of, and detected by, at least one of the ATC radars serv-
ing the GBT in use.
Only transponder-equipped targets (i.e., Mode A/C or Mode S transponders) are detected. Current radar siting
may result in limited radar surveillance coverage at lower altitudes near some general aviation airports, with
subsequently limited TIS-B Service volume coverage. If there is no radar coverage in a given area, then there
will be no TIS-B coverage in that area.
ADS-B Traffic