NORBIT iWBMS - Page 114

10.4.3 User Manual Contents April 17, 2020
Firmware: 5.2.1 Page 114 of 142
Nav Status
Description
DR (Dead
Reckoning)
No GNSS input is available; navigation is using only the IMU data
RTCM DGNSS
Navigator is tightly coupled using the primary GNSS raw observables plus base
GNSS corrections (RTCM 1 or 9)
CODE DGNSS
Navigator is tightly coupled using the primary GNSS raw observables plus base
GNSS corrections (RTCM 18 and 19, CMR, CMR+)
FLOAT RTK
Navigator is tightly coupled using the primary GNSS raw observables plus base
GNSS corrections (RTCM 18 and 19, CMR, CMR+)
FIXED RTK
Same as Float RTK but better accuracy
Pri. C/A
Navigator is closely coupled using the primary GNSS position data in C/A mode
Pri. DGNSS
Navigator is closely coupled using the primary GNSS position data in DGNSS mode
Pri. P Code
Navigator is closely coupled using the primary GNSS position data in P-CODE mode
Pri. FIXED /
FLOAT RTK
Navigator is closely coupled using the primary GNSS position data in RTK mode
Aux. DGNSS
Navigator is loosely coupled using the auxiliary GNSS position data in DGNSS mode
Aux. P Code
Navigator is loosely coupled using the auxiliary GNSS position data in P-CODE mode
Aux. Float RTK
Navigator is loosely coupled using the auxiliary GNSS position data in Float RTK
mode
Aux. WL RTK
Navigator is loosely coupled using the auxiliary GNSS position data in Wide Lane
RTK mode
Aux. NL RTK
Navigator is loosely coupled using the auxiliary GNSS position data in Narrow Lane
RTK mode
Decoupled IMU Mounting
In some scenarios, it may be required that the IMU be decoupled from the sonar and mounted
elsewhere on the survey vessel. This requires additional offsets that are not required for a typical
iWBMS installation. Depending on the IMU mounting location, additional offsets may include IMU to
vessel center of rotation (CoR) and CoR to sonar phase center. Should the user decide to use the
IMU as the vessel reference then the IMU to CoR offset is not needed.
To decouple the WBMS from the IMU start by removing the four bolts at the back of the iWBMS
bracket. This should be done with the iWBMS resting on a padded surface to reduce the chances of
damage. Once the 4 bolts are removed carefully separate the IMU from the sonar taking care to not
lose the dowel nuts located in the base plate of the IMU.
For mounting the IMU, NORBIT provides an optional mounting plate that mounts the IMU (shown in
the appendix) in its NORBIT housing, with the connector facing towards the bow of the survey vessel.
In this mounting configuration there is a +90° Z axis rotation.
Should the user opt to mount the IMU without the optional NORBIT mounting plate the dowel nuts
can be used. This requires that the IMU be secured to a mounting location that facilitates tightening
the mounting screw from underneath. The utilized screws should be M6 and of an enough length to
extend 23mm from the top of the mounting plate for securing the IMU.