Kongsberg Simrad ES80, Installation Manual, Page: 192 / 312

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Example
If you wish to measure the actual water depth, you will need to know the vertical
distance from the echo sounder transducer to the water line. Since the vessel’s
displacement changes with the amount of cargo, fuel etc, the physical location of
the water line on the hull must either be measured at a regular basis, or measured
with a second sensor.
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.
A 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).
B
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).
C
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).
D 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)
Simrad ES80 Installation Manual