Inserting the installation parameters for the motion reference unit (MRU)
The physical location of the motion reference unit (MRU) relative to the transducer is required to allow the ME70 system to adjust for roll and pitch as accurately as possible.
Prerequisites
The relevant offset values can normally be taken from the vessel drawings. The information about the installation angles must be retrieved from the reports provided by the personnel that installed the equipment. For maximum accuracy, we strongly recommend that you use the information provided by a dimensional survey.
Note
Determining the relative positions and orientations of the sensors and the transducer with high accuracy is important. This requires professional land surveying done by qualified and trained surveyors using proven survey equipment and methods. We recommend that you use third-party consultants with well proven experience with vessel dimensional control. The information provided by the dimensional survey is entered into the ME70 software as installation parameters.
Neither tools nor instruments are required. The ME70 system is turned on and operates normally.
Context
The motion reference unit (MRU) measures the roll and pitch movements of the vessel. Some sensor models also measure heave.
You must insert the physical location of the motion reference unit related to the reference point (origin) you created on the Ship page. The values for rotation around the X, Y and Z axis are used to compensate for any misalignments made during the physical installation of the motion reference unit. Such misalignments occur if the sensor is not placed in parallel with the vessel’s horizontal and/or vertical planes. The required accuracy of the offset and rotation angles depends on the accuracy requirements for the echo data.
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A Rotation around the x-axis: In the positive horizontal direction (forward), a positive rotation is clockwise.
B Rotation around the y-axis: In the positive horizontal direction (starboard), a positive rotation is clockwise.
C Rotation around the z-axis: In the positive vertical direction (down), a positive rotation is clockwise.
D Reference point (Ship Origin)
Note
The Kongsberg Seapath® - and other GPS systems - allow you to define the MRU location in the positioning system. If this is done, the MRU offset values in the ME70 system must be set to 0 (zero) to avoid "dual compensation". The rotation angles are normally not recorded by the positioning system.
Procedure
1 Open the Setup menu.
2 On the Setup menu, select Installation.
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Observe that the Installation dialog box opens. This dialog box contains a number of pages selected from the menu on the left side.
3 On the left side of the Installation dialog box, select the small white triangle next to Installation Parameters.
Observe that a menu opens with access to all the individual pages.
4 Select MRU to open the page.
a From the dimensional survey report, extract the relevant information.
b Insert the correct values. Do this as accurately as possible.
c Record the information in the result table.
5 At the bottom of the page, select Apply to save your settings.
6 Continue your work in the Installation dialog box, or select OK to close it.
Result
Motion reference unit (MRU) offsets
X Offset  
Y Offset  
Z Offset  
Installation angle X (αX)  
Installation angle Y (αY)  
Installation angle Z (αZ)