Installation Alignment Packet
| Installation Alignment Packet | ||||
|---|---|---|---|---|
| Packet ID | 185 | |||
| Length | 73 | |||
| Read / Write | Read / Write | |||
| 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 |
|
| 12 | 41 | fp32 | 4 |
|
| 13 | 45 | fp32 | 4 | GNSS antenna offset Z (m) |
| 14 | 49 | fp32 | 4 | Odometer offset X (m)1 |
| 15 | 53 | fp32 | 4 | Odometer offset Y (m)1 |
| 16 | 57 | fp32 | 4 | Odometer offset Z (m)1 |
| 17 | 61 | fp32 | 4 | External data offset X (m)2 |
| 18 | 65 | fp32 | 4 | External data offset Y (m)2 |
| 19 | 69 | fp32 | 4 | External data offset Z (m)2 |
| 1Odometer offset is used for Odometer and DVL input |
||||
| 2External data offset is used for NMEA input, External GNSS and Air Data Unit | ||||
Installation Alignment Packet
Alignment DCM
The alignment DCM (Direction Cosine Matrix) is used to represent an alignment offset of Certus from its standard alignment. A DCM is used rather than Euler angles for accuracy reasons. To convert Euler angles to DCM, 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)
DCM[1][2] = cos(pitch) * sin(roll)
DCM[2][0] = sin(heading) * sin(roll) + cos(heading) * sin(pitch) * cos(roll)
DCM[2][1] = -cos(heading) * sin(roll) + sin(heading) * sin(pitch) * cos(roll)
DCM[2][2] = cos(pitch) * cos(roll)