ALMANAC
Decoded GPS L1 C/A Almanac
|
Platform: |
OEM719, OEM729, OEM7500, OEM7600, OEM7700, OEM7720, PwrPak7, CPT7, CPT7700, SMART7, SMART2 |
This log contains the decoded GPS almanac parameters from L1 C/A subframes four and five, as received from the satellite, with the parity information removed and appropriate scaling applied. For more information about almanac data, refer to the GPS SPS Signal Specification.
The OEM7 family of receivers automatically save almanacs in their Non-Volatile Memory (NVM), so creating an almanac boot file is not necessary.
Message ID: 73
Log Type: Asynch
Recommended Input:
log almanaca onchanged
ASCII Example:
#ALMANACA,USB1,0,65.5,SATTIME,2209,494970.000,02000020,06de,16809;
31,
1,2210,61440.0,1.189947e-02,-7.49745516e-09,2.7464570e+00,9.04911221e-01,
5.43628036e-01,3.62396240e-04,-7.27595761e-12,1.45857660e-04,2.6559901e+07,
4.54861256e-02,3,0,0,TRUE,
2,2210,61440.0,2.042484e-02,-7.79461039e-09,2.6553604e+00,-1.4191382e+00,
6.98451114e-01,-6.53266907e-04,0.00000000,1.45858448e-04,2.6559805e+07,
2.35789625e-02,1,0,0,TRUE,
3,2210,61440.0,4.142284e-03,-7.64603277e-09,-2.5031848e+00,9.52756366e-01,
-5.65670396e-01,-2.45094299e-04,-1.45519152e-11,1.45862179e-04,2.6559352e+07,
3.12788270e-02,3,0,0,TRUE,
...
30,2210,61440.0,5.815029e-03,-7.89747182e-09,-3.91536612e-01,-2.6938085e+00,
-1.35149100e-01,-5.28335571e-04,0.00000000,1.45850074e-04,2.6560822e+07,
-6.21981273e-03,3,0,0,TRUE,
31,2210,61440.0,1.043320e-02,-7.71460706e-09,-3.84896228e-01,3.90039333e-01,
-5.91707997e-01,-1.77383423e-04,0.00000000,1.45852520e-04,2.6560525e+07,
1.28291128e-02,2,0,0,TRUE,
32,2210,61440.0,5.961895e-03,-8.08033658e-09,-1.4636431e+00,-2.2868654e+00,
-2.8675969e+00,-1.27792358e-04,-7.27595761e-12,1.45866076e-04,2.6558879e+07,
1.52259577e-02,3,0,0,TRUE*0eadcab6
The speed at which the receiver locates and locks onto new satellites is improved if the receiver has approximate time and position (SETAPPROXTIME and SETAPPROXPOS), as well as an almanac. This allows the receiver to compute the elevation of each satellite so it can tell which satellites are visible and their Doppler offsets, improving Time to First Fix (TTFF).
|
Field |
Field type |
Description |
Format |
Binary Bytes |
Binary Offset |
|---|---|---|---|---|---|
|
1 |
Log header |
ALMANAC header For information about log headers, see ASCII, Abbreviated ASCII or Binary. |
|
H |
0 |
|
2 |
#messages |
The number of satellite PRN almanac messages to follow. Set to zero until almanac data is available |
Long |
4 |
H |
|
3 |
PRN |
Satellite PRN number for current message (dimensionless) |
Ulong |
4 |
H+4 |
|
4 |
week |
Almanac reference week (GPS reference week number) |
Ulong |
4 |
H+8 |
|
5 |
seconds |
Almanac reference time (seconds into the week) |
Double |
8 |
H+12 |
|
6 |
ecc |
Eccentricity (dimensionless) |
Double |
8 |
H+20 |
|
7 |
ώ |
Rate of right ascension (radians/second) |
Double |
8 |
H+28 |
|
8 |
ωo |
Right ascension (radians) |
Double |
8 |
H+36 |
|
9 |
ω |
Argument of perigee (radians) |
Double |
8 |
H+44 |
|
10 |
Mo |
Mean anomaly of reference time (radians) |
Double |
8 |
H+52 |
|
11 |
afo |
Clock aging parameter (seconds) |
Double |
8 |
H+60 |
|
12 |
af1 |
Clock aging parameter (seconds/second) |
Double |
8 |
H+68 |
|
13 |
N0 |
Computed mean motion (radians/second) |
Double |
8 |
H+76 |
|
14 |
A |
Semi-major axis (metres) |
Double |
8 |
H+84 |
|
15 |
incl-angle |
Angle of inclination relative to 0.3 π (radians) |
Double |
8 |
H+92 |
|
16 |
SV config |
Satellite configuration |
Ulong |
4 |
H+100 |
|
17 |
health-prn |
SV health from Page 25 of subframe 4 or 5 (6 bits) |
Ulong |
4 |
H+104 |
|
18 |
health-alm |
SV health from almanac (8 bits) |
Ulong |
4 |
H+108 |
|
19 |
antispoof |
Anti-spoofing on? 0 = FALSE 1 = TRUE |
Bool |
4 |
H+112 |
|
20... |
Next PRN offset = H + 4 + (#messages x 112) |
||||
|
21 |
xxxx |
32-bit CRC (ASCII and Binary only) |
Hex |
4 |
H + 4 +(112 x #messages) |
|
22 |
[CR][LF] |
Sentence terminator (ASCII only) |
- |
- |
- |