Maretron SSC200 用户手册
Revision 1.8
Page 13
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2. With the vessel laying flat in the water, adjust the pitch angle of the SSC200 by adding
small washers or spacers between the mounting bracket holes and mounting surface
until the display reads zero for the pitch angle (skip this step if you are not interested in
viewing the vessel’s pitch angle).
until the display reads zero for the pitch angle (skip this step if you are not interested in
viewing the vessel’s pitch angle).
3. With the vessel laying flat in the water on a known heading, adjust the heading of the
SSC200 by rotating it until the display reads the known vessel heading.
4. Recheck that the roll and pitch readings are zero and that the indicated heading is
correct (repeat steps 1 through 3 as necessary).
5. Securely fasten the SSC200 by tightening the mounting screws.
4 Variation
Variation is the angular difference between the true meridian (great circle connecting the
geographic poles) and the magnetic meridian (direction of the lines of magnetic flux). Variation
has different values at different locations on the earth with most areas undergoing change to
the variation over time.
Normally, heading information is displayed as either a “true” heading (a direction relative to the
geographic poles) or it is displayed as a “magnetic” heading (a direction relative to the lines of
magnetic flux). North-seeking gyrocompasses are capable of measuring direction relative to
the geographic poles (“true”) whereas magnetic compasses measure direction relative to the
earth’s local magnetic flux (“magnetic”).
The SSC200 is a magnetic compass; therefore, it requires an external source for variation if
you want to view your heading in “true” format. The SSC200 is capable of receiving variation in
one of three ways; 1) via the NMEA 0183 interface, 2) via the NMEA 2000
geographic poles) and the magnetic meridian (direction of the lines of magnetic flux). Variation
has different values at different locations on the earth with most areas undergoing change to
the variation over time.
Normally, heading information is displayed as either a “true” heading (a direction relative to the
geographic poles) or it is displayed as a “magnetic” heading (a direction relative to the lines of
magnetic flux). North-seeking gyrocompasses are capable of measuring direction relative to
the geographic poles (“true”) whereas magnetic compasses measure direction relative to the
earth’s local magnetic flux (“magnetic”).
The SSC200 is a magnetic compass; therefore, it requires an external source for variation if
you want to view your heading in “true” format. The SSC200 is capable of receiving variation in
one of three ways; 1) via the NMEA 0183 interface, 2) via the NMEA 2000
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interface, or 3)
through manual variation entry.
Normally, the SSC200 will automatically use variation from either the NMEA 0183 interface or
the NMEA 2000
Normally, the SSC200 will automatically use variation from either the NMEA 0183 interface or
the NMEA 2000
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interface, however, you can force the SSC200 to use variation from only the
NMEA 0183 interface or you can force the SSC200 to use variation from only the NMEA 2000
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interface or you can force SSC200 to only use manually entered variation.
WARNING: Multiple variation sources that are received by the SSC2000 (i.e., NMEA 0183
and NMEA 2000
WARNING: Multiple variation sources that are received by the SSC2000 (i.e., NMEA 0183
and NMEA 2000
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interfaces) will cause confusion as to the correct source to be used for
true heading indications. If more than one variation source is available, then the SSC200
needs to be programmed to use the appropriate source for reporting subsequent true
heading information. See Section 4.4 for details on choosing a specific variation source
when more than one variation source is available.
needs to be programmed to use the appropriate source for reporting subsequent true
heading information. See Section 4.4 for details on choosing a specific variation source
when more than one variation source is available.
4.1 Variation Input via NMEA 0183 Interface
As shipped from the factory, the SSC200 automatically looks for variation data coming from
the NMEA 0183 interface. The SSC200 accepts variation data from the Recommended
Minimum Specific GNSS Data (RMC) sentence or the SSC200 computes variation from the
Course Over Ground and Ground Speed (VTG) sentence. If the SSC200 does indeed receive
variation information from the NMEA 0183 interface, then it will do the following:
the NMEA 0183 interface. The SSC200 accepts variation data from the Recommended
Minimum Specific GNSS Data (RMC) sentence or the SSC200 computes variation from the
Course Over Ground and Ground Speed (VTG) sentence. If the SSC200 does indeed receive
variation information from the NMEA 0183 interface, then it will do the following: