Technical Provisions for Mode S Services and Extended Squitter

Appendix A A-41
MB FIELD
DRAFT - Working Paper ASP TSGWP11-01 for review by the TSG during the meeting in June 2011 in Paris
Table A-2-5. BDS code 0,5 — Extended squitter airborne position
1 MSB
2 FORMAT TYPE CODE
3
4
(specified in §A.2.3.1)
5 LSB
6 MSB SURVEILLANCE STATUS
7 LSB (specified in §A.2.3.2.6)
8 SINGLE ANTENNA FLAG (SAF) (specified in §A.2.3.2.5)
9
10
11
MSB
12 ALTITUDE
13
14
15
(specified by the FORMAT TYPE CODE)
16 This is (1) the altitude code (AC) as specified in
17 §3.1.2.6.5.4 of Annex 10, Volume IV, but with the
18
19
M-bit removed, or (2) the GNSS height (HAE)
20 LSB
21 TIME (T) (specified in §A.2.3.2.2)
22 CPR FORMAT (F) (specified in §A.2.3.2.1)
23
24
25
26
27
28
29
MSB
30 ENCODED LATITUDE
31
32
33
34
35
36
37
38
(CPR airborne format specified in §AC.2.6)
39 LSB
40
41
42
43
44
45
46
MSB
47 ENCODED LONGITUDE
48
49
50
51
52
53
54
55
(CPR airborne format specified in §AC.2.6)
56 LSB
PURPOSE: To provide accurate airborne position information.
Surveillance status shall be coded as follows:
0 = No condition
1 = Permanent alert (emergency condition)
2 = Temporary alert (change in Mode A identity code other
than emergency condition)
3 = SPI condition
Codes 1 and 2 shall take precedence over code 3.
When horizontal position information is unavailable, but altitude
information is available, the airborne position message shall be
transmitted with a format TYPE Code of ZERO (0) in bits 1 — 5
and the barometric pressure altitude in bits 9 to 20. If neither
horizontal position nor barometric altitude information is available,
then all 56 bits of transponder register 0516 shall be zeroed. The
ZERO format TYPE Code field shall indicate that latitude and
longitude information is unavailable, while the ZERO altitude field
shall indicate that altitude information is unavailable.
Draft
DRAFT - Working Paper ASP TSGWP11-01 for review by the TSG during the meeting in June 2011 in Paris