GNSS Compass Reference Manual
Page 77 of 85
Version 1.1
13/01/2021
10.11.4
Installation Alignment Packet
Installation Alignment Packet
Packet ID
185
Length
73
Field #
Bytes
Offset
Data
Type
Size
Description
1
0
u8
1
Permanent
2
1
fp32
4
Alignment DCM[0][0]
3
5
fp32
4
Alignment DCM[0][1]
4
9
fp32
4
Alignment DCM[0][2]
5
13
fp32
4
Alignment DCM[1][0]
6
17
fp32
4
Alignment DCM[1][1]
7
21
fp32
4
Alignment DCM[1][2]
8
25
fp32
4
Alignment DCM[2][0]
9
29
fp32
4
Alignment DCM[2][1]
10
33
fp32
4
Alignment DCM[2][2]
11
37
fp32
4
GNSS antenna offset X (m)
12
41
fp32
4
GNSS antenna offset Y (m)
13
45
fp32
4
GNSS antenna offset Z (m)
14
49
fp32
4
Odometer offset X (m)
15
53
fp32
4
Odometer offset Y (m)
16
57
fp32
4
Odometer offset Z (m)
17
61
fp32
4
External data offset X (m)
18
65
fp32
4
External data offset Y (m)
19
69
fp32
4
External data offset Z (m)
Table 97: Installation alignment packet
10.11.4.1
Alignment DCM
The alignment DCM (direction cosine matrix) is used to represent an alignment offset of GNSS
Compass from it's standard alignment. A DCM is used rather than euler angles for accuracy
reasons. To convert euler angles to DCM please use the formula below with angles in radians.
DCM[0][0] = cos(heading) * cos(pitch)
DCM[0][1] = sin(heading) * cos(pitch)
DCM[0][2] = -sin(pitch)
DCM[1][0] = -sin(heading) * cos(roll) + cos(heading) * sin(pitch) * sin(roll)
DCM[1][1] = cos(heading) * cos(roll) + sin(heading) * sin(pitch) * sin(roll)
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