Kongsberg Simrad EK80 Installation Manual page 185

In order to establish a system
to measure the relative
distance between sensors, a
virtual coordinate system is
established. This coordinate
system uses three vectors; X,
Y and Z.
The X-axis is the
A
longitudinal direction
of the vessel, and in
parallel with the deck.
A positive value for X means that a sensor or a reference point is located ahead
of the reference point (origin).
The Y-axis is the transverse direction of the vessel, and in parallel with the deck.
B
A positive value for Y means that a sensor or a reference point is located on the
starboard side of the reference point (origin).
The Z-axis is vertical, and in parallel with the mast. A positive value for Z means
C
that a sensor or a new reference point is located under the reference point (origin).
Reference point (Ship Origin)
D
Coordinate system origin
The origin is the common reference point where all three axis in the vessel coordinate
system meet. All physical locations of the vessel's sensors (radar and positioning
system antennas, echo sounder and sonar transducers, motion reference units, etc.) are
referenced to the origin. In most cases, the location of the vessel's "official" origin
has been defined by the designer or shipyard. This origin is normally identified with a
physical marking, and also shown on the vessel drawings.
Frequently used locations are:
• Aft immediately over the rudder (frame 0)
• Vessel's centre of gravity
• The physical location of the motion reference unit (MRU)
Coordinate system alternative origins
If necessary, other origin locations may be defined for specific products or purposes. One
example is the Navigation Reference Point that is frequently used. Whenever a vessel
is surveyed to establish accurate offset information, the surveyor may also establish an
alternative origin location. Whenever relevant, any such alternative locations must
be defined using offset values to the "official" origin established by the designer or
shipyard. A commonly used alternative origin is the physical location of the vessel's
motion reference unit (MRU).
394149/D
Dimensional surveying
183