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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-7<br />

B.2.3.3.2 HEADING/GROUND TRACK<br />

B.2.3.3.2.1 Heading/ground track status<br />

This 1-bit field shall define the validity of the heading/ground track value. Coding <strong>for</strong> this field shall be as follows:<br />

0=invalid <strong>and</strong> 1=valid.<br />

Note.— If a source of A/V heading is not available to the ADS-B transmitting subsystem, but a source of ground<br />

track angle is available, then ground track angle may be used instead of heading, provided that the status bit <strong>for</strong> heading<br />

subfield is set to ZERO (0) whenever the ground track angle is not a reliable indication of the A/V’s Heading. (The<br />

ground track angle is not a reliable indication of the A/V’s heading when the A/V’s ground speed is low.)<br />

B.2.3.3.2.2 Heading/ground track value<br />

This 7-bit (14-20) field shall define the direction (in degrees clockwise from true or magnetic north) of aircraft motion on<br />

the surface. The value shall be encoded as an unsigned angular weighted binary numeral, with an MSB of 180 degrees<br />

<strong>and</strong> an LSB of 360/128 degrees, with zero indicating true north. The data in the field shall be rounded to the nearest<br />

multiple of 360/128 degrees.<br />

Note.— The reference direction <strong>for</strong> heading (whether true north or magnetic north) is indicated in the horizontal<br />

reference direction (HRD) field of the aircraft operational status message (see §B.2.3.10.13).<br />

B.2.3.3.3 COMPACT POSITION REPORTING (CPR) FORMAT (F)<br />

The CPR <strong>for</strong>mat field shall be <strong>for</strong>matted as specified in §A.2.3.3.3.<br />

B.2.3.3.4 TIME SYNCHRONIZATION (T)<br />

Draft<br />

The time synchronization field shall be <strong>for</strong>matted as specified in §A.2.3.3.4.<br />

B.2.3.3.5 LATITUDE/LONGITUDE<br />

The latitude/longitude field shall be <strong>for</strong>matted as specified in §A.2.3.3.5.<br />

B.2.3.4 IDENTIFICATION AND CATEGORY FORMAT<br />

The identification <strong>and</strong> category squitter shall be <strong>for</strong>matted as specified in §A.2.3.4.<br />

B.2.3.5 AIRBORNE VELOCITY FORMAT<br />

The airborne velocity squitter shall be <strong>for</strong>matted as specified in the definition of register number 0916 <strong>and</strong> in the following<br />

paragraphs.<br />

DRAFT - Working Paper ASP TSGWP11-01 <strong>for</strong> review by the TSG during the meeting in June 2011 in Paris

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