GPS ephemeris report
The 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 one (1) to request the report. The first following table shows the additional records provided in Report Packet 55h when ephemeris data is included.
The 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. The ephemeris flags are described in the second following table.
|
Subtype 1: GPS ephemeris data |
||||
|---|---|---|---|---|
|
Byte |
Item |
Type |
Value |
Meaning |
|
6–7 |
EPHEMERIS WEEK # |
2 (short) |
GPS ICD-200 |
Ephemeris week number |
|
8–9 |
IODC |
2 (short) |
GPS ICD-200 |
|
|
10 |
RESERVED |
1 (byte) |
GPS ICD-200 |
|
|
11 |
IODE |
1 (byte) |
GPS ICD-200 |
|
|
12–15 |
TOW |
4 (long) |
GPS ICD-200 |
|
|
16–19 |
TOC |
4 (long) |
GPS ICD-200 |
|
|
20–23 |
TOE |
4 (long) |
GPS ICD-200 |
|
|
24–31 |
TGD |
8 (double) |
GPS ICD-200 |
|
|
32–39 |
AF2 |
8 (double) |
GPS ICD-200 |
|
|
40–47 |
AF1 |
8 (double) |
GPS ICD-200 |
|
|
48–55 |
AF0 |
8 (double) |
GPS ICD-200 |
|
|
56–63 |
CRS |
8 (double) |
GPS ICD-200 |
|
|
64–71 |
DELTA N |
8 (double) |
GPS ICD-200 |
|
|
72–79 |
M SUB 0 |
8 (double) |
GPS ICD-200 |
|
|
80–87 |
CUC |
8 (double) |
|
Multiply by π to obtain ICD units |
|
88–95 |
ECCENTRICITY |
8 (double) |
GPS ICD-200 |
|
|
96–103 |
CUS |
8 (double) |
|
Multiply by π to obtain ICD units |
|
104–111 |
SQRT A |
8 (double) |
GPS ICD-200 |
|
|
112–119 |
CIC |
8 (double) |
|
Multiply by π to obtain ICD units |
|
120–127 |
OMEGA SUB 0 |
8 (double) |
GPS ICD-200 |
|
|
128–135 |
CIS |
8 (double) |
|
Multiply by π to obtain ICD units |
|
136–143 |
I SUB 0 |
8 (double) |
GPS ICD-200 |
|
|
144–151 |
CRC |
8 (double) |
GPS ICD-200 |
|
|
152–159 |
OMEGA |
8 (double) |
GPS ICD-200 |
|
|
160–167 |
OMEGA DOT |
8 (double) |
GPS ICD-200 |
|
|
168–175 |
I DOT |
8 (double) |
GPS ICD-200 |
|
|
176–179 |
FLAGS |
4 (double word) |
GPS ICD-200 |
|
|
---------- End of Subtype 1 ---------- |
||||
Where FLAGS is encoded as a 32-bit value given by the following table:
|
Bit(s) |
Description |
Location |
|---|---|---|
|
0 |
Data flag for L2 P-code |
Sub 1, word 4, bit 1 |
|
1–2 |
Codes on L2 channel |
Sub 1, word 3, bits 11–12 |
|
3 |
Anti-spoof flag: Y-code on: from ephemeris |
Sub 1–5, HOW, bit 19 |
|
4–9 |
SV health: from ephemeris |
Sub 1, word 3, bits 17–22 |
|
10 |
Fit interval flag |
Sub 2, word 10, bit 17 |
|
11–14 |
URA: User Range Accuracy |
Sub 1, word 3, bits 13–16 |
|
15 |
URA may be worse than indicated Block I: Momentum Dump flag |
Sub 1–5, HOW, bit 18 |
|
16–18 |
SV Configuration: SV is Block I or Block II |
Sub 4, page 25, word and bit depends on SV |
|
19 |
Anti-spoof flag: Y-code on |
Sub 4, page 25, word and bit depends on SV |