Geo-Referencing Radar Plot Data for the Traffic Information Service Broadcast

The Federal Aviation Administration (FAA) has gained some significant early operational experience with the Traffic Information Service Broadcast (TIS-B), both on the East Coast of the United States, and in the Anchorage, Alaska area. TIS-B, for the first time, puts geo-referenced radar data directly in the cockpit where, for a number of reasons, the customer can be more sensitive to inaccuracy and other anomalies than the traditional user (i.e., the air traffic controller). The Broadcast of Automatic Dependent Surveillance (ADS-B) is the air-to-air transmission of aircraft position and velocity information. In order for ground surveillance radar data and ADS-B data to integrate seamlessly in the cockpit, a "truly geo-referenced" radar alignment technique is needed for radar to ADS-B correlation. Successful synergy between ADS-B and radar requires accrued radar registration. Incorrect geo-referencing can result in a number of anomalies that can be difficult for both designers and pilots to deal with appropriately. This paper describes the process of georeferencing radar data, describes some real world limitations of the radar sensors, the anomalies that can be encountered and their cause, techniques for mitigating these anomalies, and finally, this paper discusses one of the radar alignment techniques used for the system providing TIS-B in Anchorage for the FAA's Capstone program. This paper will attempt to bridge the gap between the ground systems and airborne systems. Given the insight into the processing performed on the ground, the avionics developers may adapt or create new ways to overcome these issues.