BeiDou ephemeris report

The BeiDou ephemeris report is sent when Command Packet 54h is used to request the ephemeris for one satellite or all satellites. The GETSVDATA SUBTYPE byte (byte 4) is set to twenty-one (21) to request the report. The first table below shows the additional records provided in Report Packet 55h when ephemeris data is included.

The Beidou ephemeris data follows the standard defined by GPS ICD-200 except for CUC, CUS, CIS, and CIC. These values must be multiplied by π to become the units specified in the GPS ICD-200 document.

Subtype 21: BeiDou ephemeris data
Byte	Item	Type	Value	Meaning
6–7	WEEK NUMBER	2 (short)		GPS Time
8–9	IODC	2 (short)
10	RESERVED	1 (byte)
11	IODE	1 (byte)
12–15	TOW	4 (long)		seconds (GPS Time)
16–19	TOC	4 (long)		seconds (GPS Time)
20–23	TOE	4 (long)		seconds (GPS Time)
24–31	TGD	8 (double)		seconds
32–39	AF2	8 (double)		seconds/second2
40–47	AF1	8 (double)		seconds/second
48–55	AF0	8 (double)		seconds
56–63	CRS	8 (double)		meters
64–71	DELTA N	8 (double)		semi-circles/sec
72–79	M SUB 0	8 (double)		semi-circles
80–87	CUC	8 (double)		semi-circles (multiply by π to obtain ICD units)
88–95	ECCENTRICITY	8 (double)
96–103	CUS	8 (double)		semi-circles (multiply by π to obtain ICD units)
104–111	SQRT A	8 (double)		sqrt (meters)
112–119	CIC	8 (double)		semi-circles (multiply by π to obtain ICD units)
120–127	OMEGA SUB 0	8 (double)		semi-circles
128–135	CIS	8 (double)		semi-circles (multiply by π to obtain ICD units)
136–143	I SUB 0	8 (double)		semi-circles
144–151	CRC	8 (double)		meters
152–159	OMEGA	8 (double)		semi-circles
160–167	OMEGA DOT	8 (double)		semi-circles/sec
168–175	I DOT	8 (double)		semi-circles/sec
176–179	FLAGS	4 (double word)
---------- End of Subtype 21 ----------

Where FLAGS is encoded as a 32-bit value given by the following table:

Bit(s)	Description
0	TGD2 Loaded (1= loaded)
1–3	Spare
4	health Bit
5–10	Spare
11–14	URAI (BeiDou version of UDRE)
15	Spare
16–25	TGD2 (all zeros if not loaded) – units 0.1 ns
26–31	Spare