Technical Provisions for Mode S Services and Extended Squitter
Technical Provisions for Mode S Services and Extended Squitter
Technical Provisions for Mode S Services and Extended Squitter
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DRAFT - Working Paper ASP TSGWP11-01 <strong>for</strong> review by the TSG during the meeting in June 2011 in Paris<br />
Appendix B B-5<br />
Note 9.— Version 1 position messages with Type Codes 8, 18, or 22, <strong>and</strong> position messages associated with SIL of<br />
0 or NACP of 0 are not appropriate to support most ADS-B applications since the accuracy or integrity of the position<br />
broadcast in these messages is unknown by the transmitting device.<br />
Note 10.— It is recommended that Version 1 extended squitter messages with unknown accuracy or integrity only<br />
be used if either the position accuracy or integrity can be verified by other means, or the application has no specific<br />
requirements <strong>for</strong> these parameters.<br />
B.2.3.1.1 AIRBORNE POSITION MESSAGE TYPE CODE<br />
B.2.3.1.1.1 Airborne position message TYPE Code if containment radius is available<br />
Note.— If the position in<strong>for</strong>mation comes from a GNSS receiver that con<strong>for</strong>ms to the ARINC 743A Characteristic, a<br />
suitable source of in<strong>for</strong>mation <strong>for</strong> the containment radius (RC), is ARINC 429 label 130 from that GNSS receiver.<br />
If RC (containment radius) in<strong>for</strong>mation is available from the navigation data source, then the transmitting ADS-B<br />
subsystem shall determine the TYPE Code (the value of the TYPE subfield) of airborne position messages as follows.<br />
a) If current valid horizontal position in<strong>for</strong>mation is not available to the ADS-B Transmitting Subsystem, then the<br />
TYPE subfield of Airborne Position Messages shall be set to ZERO (0).<br />
b) If valid horizontal position <strong>and</strong> barometric pressure-altitude in<strong>for</strong>mation are both available to the ADS-B<br />
Transmitting Subsystem, then the ADS-B Transmitting Subsystem shall set the TYPE subfield of Airborne<br />
Position Messages to a value in the range from 9 to 18 in accordance with the table of §B.2.3.1.<br />
c) If valid horizontal position in<strong>for</strong>mation is available to the ADS-B Transmitting Subsystem, but valid barometric<br />
pressure-altitude in<strong>for</strong>mation is not available, <strong>and</strong> valid geometric altitude in<strong>for</strong>mation is available, the ADS-B<br />
Transmitting Subsystem shall set the TYPE subfield of Airborne Position Messages to a value in the range from<br />
20 to 22 depending on the containment radius RC <strong>and</strong> vertical protection limit VPL in accordance with the table<br />
of §B.2.3.1.<br />
d) If valid horizontal position in<strong>for</strong>mation is available to the ADS-B Transmitting Subsystem, but neither valid<br />
barometric altitude in<strong>for</strong>mation nor valid geometric altitude in<strong>for</strong>mation is available, the ADS-B Transmitting<br />
Subsystem shall set the TYPE subfield in Airborne Position Messages to a value in the range from 9 to 18<br />
depending on the containment radius RC in accordance with the table of §B.2.3.1. (In that case, the ALTITUDE<br />
subfield of the Airborne Position Messages would be set to all ZEROs in order to indicate that valid altitude<br />
in<strong>for</strong>mation is not available.)<br />
Draft<br />
B.2.3.1.1.2 Airborne position message TYPE Code if containment radius is not available<br />
If RC (containment radius) in<strong>for</strong>mation is NOT available from the navigation data source, then the ADS-B Transmitting<br />
Subsystem shall indicate NIC=0 by selecting a TYPE Code of 0, 18, or 22 in the Airborne Position Messages, as follows:<br />
a) the ADS-B Transmitting Subsystem shall set the TYPE subfield to ZERO (0) if valid horizontal position<br />
in<strong>for</strong>mation is not available; <strong>and</strong><br />
b) the ADS-B Transmitting Subsystem shall set the TYPE subfield to 18 if valid pressure-altitude in<strong>for</strong>mation is<br />
available, or if neither valid pressure-altitude nor valid geometric altitude in<strong>for</strong>mation is available.<br />
If valid pressure-altitude is not available, but valid geometric altitude in<strong>for</strong>mation is available, the ADS-B Transmitting<br />
Subsystem shall set the TYPE subfield to 22.<br />
DRAFT - Working Paper ASP TSGWP11-01 <strong>for</strong> review by the TSG during the meeting in June 2011 in Paris