Kongsberg Simrad SN90, Installation Manual

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381298/C
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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).
Defining the physical location of each sensor
By means of the vessel coordinate system, the physical location of every sensor can
be defined using three numerical values for X, Y and Z. These values must define the
vertical and horizontal distances from a single reference point; the origin. The physical
location of the motion reference unit (MRU) is often the most important sensor to define.
For many systems, the vessel heading is also a critical measurement.
+Y
+Z
+X
(CD010101_300_021)
In this example, a second reference point has been
established. It is defined with three positive offset values
for X, Y and Z. All values are positive because the new
reference point is in front of and below the origin, and on
the starboard side.
The accuracy of the three
numerical values for
X, Y and Z defines the
accuracy of the sensor
data. If you require a high
accuracy, for example for
underwater positioning,
underwater mapping or
scientific measurements,
you must have each
sensor positioned
using professional land
surveying. For such
use, a good alignment
survey is critical for high
quality results. Surveys are normally done by qualified and trained surveyors using
proven survey equipment and methods.
Related topics
Defining the Sonar Reference Point, page 195
Defining the location of the motion reference unit (MRU), page 197
Defining the location of the global positioning system (GPS), page 198
Defining the location and installation angles of the transducer, page 199
Preparations