Minimum Aviation System Performance Standards for Aircraft ...

Appendix A
Page A-11
Background Application – An application that applies to all surveilled traffic of operational interest.
One or more background applications may be in use in some or all airspace (or on the ground),
but without flight crew input or automated input to select specific traffic. Background
applications include: Enhanced Visual Acquisition (EV Acq), Conflict Detection (CD), Airborne
Conflict Management (ACM), Airport Surface Situational Awareness (ASSA), and Final
Approach and Runway Occupancy Awareness (FAROA).
Barometric altitude – Geopotential altitude in the earth’s atmosphere above mean standard sea level
pressure datum plane, measured by a pressure (barometric) altimeter.
Barometric altitude error – For a given true barometric pressure, P0, the error is the difference between
the transmitted pressure altitude and the altitude determined using a standard temperature and
pressure model with P0.
Barometric Altitude Integrity Code (NICBARO) – NICBARO is a one-bit flag that indicates whether or not
the barometric pressure altitude provided in the State Vector Report has been cross-checked
against another source of pressure altitude.
Call Sign – The term “aircraft call sign” means the radiotelephony call sign assigned to an aircraft for
voice communications purposes. (This term is sometimes used interchangeably with “flight
identification” or “flight ID”). For general aviation aircraft, the aircraft call sign is normally its
national registration number; for airline and commuter aircraft, it is usually comprised of the
company name and flight number (and therefore not linked to a particular airframe); and for the
military, it usually consists of numbers and code words with special significance for the operation
being conducted.
Capability Class Codes – Codes that indicate the capability of a participant to support engagement in
various operations.
Closest Point of Approach (CPA) – The minimum horizontal distance between two aircraft during a
close proximity encounter, also know as miss distance.
Coast Interval – The maximum time interval allowed for maintaining an ADS-B report when no
messages supporting that report are received. Requirements for coast interval are typically
specified in terms of 99% probability of reception at a given range.
Cockpit Display of Traffic Information (CDTI) – The pilot interface portion of a surveillance system.
This interface includes the traffic display and all the controls that interact with such a display.
The CDTI receives position information of traffic and own-ship from the airborne surveillance
and separation assurance processing (ASSAP) function. The ASSAP receives such information
from the surveillance sensors and own-ship position sensors.
Cockpit Display of Traffic Information (CDTI) Display – A single CDTI display format. A physical
display screen may have more than one instance of a CDTI Display on it. For example, a display
with a split screen that has a Traffic Display on one half of the screen and a list of targets on the
other half has two instances of CDTI Displays.
Collision Avoidance – An unplanned maneuver to avoid a collision.
Collision Avoidance Zone (CAZ) – Zone used by the system to predict a collision or dangerously close
spacing. The CAZ is defined by the sum of Assured Collision Avoidance Distance (ACAD) and
position uncertainties.
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