Kongsberg Simrad MF90, Installation Manual

Page: 253 / 426

476671/B
251
Placing each sensor in the vessel coordinate
system
Topics
Dimensional surveying, page 251
Surveying the transducer and the navigation sensors, page 253
Example procedure, page 254
Vessel coordinate system, page 256
Dimensional surveying
Several sensors are connected to the MF90 system to make its operation as accurate as
possible. These sensors are physically located on different places on the vessel. Typical
sensors are those providing navigational information (heading, speed or geographical
position) or vessel movements in the sea (motion sensors).
In order to "move" these sensors to a common location on the vessel a vessel coordinate
system is defined. The relative location of each sensor is then measured and referenced to
this coordinate system. This is commonly referred to as dimensional surveying .
Why is this important?
When a sensor makes a measurement, the information is always related to the physical
position of the sensor. This introduces an error since this is not the physical location of
neither you nor the MF90 system. On small vessels, these measurement errors are often
negligible. On larger vessels, however, the distances between the sensors are greater, and the
errors can affect the accuracy of the MF90 system. The errors become extra noticeable when
the vessel moves in heavy seas.
Example
The antenna of a position sensor is typically mounted high above the
superstructure, while a motion sensor is located close to the vessel’s centre of
gravity. Both of these are physically positioned far away from the transducer,
which may be located closer to the bow.
If you have an echo sounder transducer located close to the bow, the measured
depth will change considerably when the bow is subjected to heave in heavy seas.
In order reduce the measurement errors you can do this:
Setting to work