GPSMAP 496 Owner’s Manual 49TIS > TIS LimitationsTIS information is collected one radar scan prior to the scan duringwhich the uplink occurs. Therefore, the surveillance informationis approximately 5 seconds old. In order to present the intrudersin a “real time” position, the TIS ground station uses a “predictivealgorithm” in its tracking software. This algorithm uses trackhistory data to extrapolate intruders to their expected positionsconsistent with the time of display in the cockpit. Occasionally,aircraft maneuvering causes this algorithm to induce errors in theGPSMAP 496 screen. These errors primarily affect relative bearinginformation and traffic target track vector (it will lag); intruderdistance and altitude remains relatively accurate and may be used toassist in “see and avoid.” Some of the more common examples ofthese errors include:When client or intruder aircraft maneuvers excessively orabruptly, the tracking algorithm can report incorrect horizontalposition until the maneuvering aircraft stabilizes.When a rapidly closing intruder is on a course that crosses theclient aircraft course at a shallow angle (either overtaking or headon) and either aircraft abruptly changes course within ¼ nm, TISmay show the intruder on the opposite side of the client than itactually is.•••These are relatively rare occurrences and are corrected in a fewradar scans once the course has stabilized.Users of TIS can render valuable assistance in the correctionof malfunctions by reporting their observations of undesirableperformance. Reporters should identify the time of observation,location, type and identity of aircraft, and describe the conditionobserved; the type of transponder processor and software in use canalso be useful information. Since TIS performance is monitoredby maintenance personnel rather than ATC, it is suggested thatmalfunctions be reported in the following ways:By telephone to the nearest Flight Service Station (FSS) facility.By FAA Form 8000-7, Safety Improvement Report, a postage-paid card designed for this purpose. These cards can be obtainedat FAA FSSs, General Aviation District Offices, Flight StandardsDistrict Offices, and General Aviation Fixed Based Operations.••