Kongsberg EM 712 Maintenance Manual page 207

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.
1 The X-axis is
the 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).
2 The Y-axis is the transverse direction of the vessel, and in parallel with the deck.
A positive value for Y means that a sensor or a reference point is located on the
starboard side of the reference point (origin).
3 The Z-axis is vertical, and in parallel with the mast. A positive value for Z means
that a sensor or a new reference point is located under the reference point (origin).
4 Reference point (Ship Origin)
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)
451106/B
Dimensional surveying and alignment
207