Data Logs
Chapter 5
WAAS G-III Reference Receiver User Manual Rev 1
97
5.5.4
ALMANACB
This log contains the complete and verified collected almanac from the L1 C/A GPS signal.
Output states
: Operational
Valid trigger
: ONNEW,
ONCE
Frequency
: When
requested,
when
the almanac has changed
Message ID
:
4097
Header Format
:
G-III Log
If the # entries field is 0, the CRC will be output directly following the # entries field.
Field
Field Name
Description
Format
# Bytes
Binary Offset
1
Header
G-III log header
H
0
2
System
System the almanac pertains to
0 = GPS
Enum
2
H
3
Reserved
Reserved
Ushort
2
H+2
4
SVused
PRN of the SV the almanac is from
Ushort
2
H+4
5
#valid
Number of almanacs used in validation
Ushort
2
H+6
6
# entries
Number of entries to follow
Ulong
4
H+8
7
PRN
PRN
Ulong
4
H+12
8
Week
Almanac reference week
Ulong
4
H+16
9
Seconds
Almanac reference time (s)
Double
8
H+20
10
Ecc
Eccentricity
Double
8
H+28
11
Dot
Rate of right ascension, radians/second
Double
8
H+36
12
o
Right ascension, radians
Double
8
H+44
13
Argument of perigee, radians
Double
8
H+52
14
M
o
Mean anomaly of reference time, radians
Double
8
H+60
15
a
fo
Clock aging parameter, seconds
Double
8
H+68
16
a
f1
Clock aging parameter, seconds/second
Double
8
H+76
17
N
Corrected mean motion, radians/second
Double
8
H+84
18
A
Semi-major axis, metres
Double
8
H+92
19
Incl-angle
Angle of inclinations relative to 0.3
, radians
Double
8
H+100
20
SV config
Satellite configuration
Ulong
4
H+108
21
Health-prn
SV health from subframe 4 or 5
Ulong
4
H+112
22
Health-alm
SV health from almanac
Ulong
4
H+116
23
antispoof
Antispoofing flag where:
0=FALSE
1=TRUE
Enum
4
H+120
24…
Next almanac data set, offset = H + 12 + (#previous msgs x 112)
Variable
32-bit CRC
Hex
4
H + 12 +
(#entries x 112)