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SSC200 User’s Manual
Page 14 Revision 1.8
1. Transmit the Heading, Deviation & Variation (HDG) sentence including the variation
field as seen from the RMC or VTG sentence over the NMEA 0183 interface if HDG is
enabled (see Appendix A for enabling or disabling NMEA 0183 sentences).
2. Transmit the Heading True (HDT) sentence using variation data from the RMC or VTG
sentence over the NMEA 0183 interface if HDT is enabled (see Appendix A for enabling
or disabling NMEA 0183 sentences).
3. Transmit over the NMEA 2000
®
interface the Magnetic Variation PGN (127258) with the
Variation Source field value corresponding to the received NMEA 0183 variation data
from the RMC or VTG sentence. The PGN’s Variation Source field will be transmitted
with the lowest possible quality indicator, which is “Manual Entry”.
4.2 Variation Input via the NMEA 2000
®
Interface
As shipped from the factory, the SSC200 automatically looks for variation data coming from
the NMEA 2000
®
interface. The SSC200 accepts variation data from the Magnetic Variation
PGN (127258). If the SSC200 does indeed receive variation information from the NMEA 2000
®
interface, then it will do the following:
1. Transmit the Heading, Deviation & Variation (HDG) sentence including the variation
field as seen from the Magnetic Variation PGN (127258) from the NMEA 2000 interface
if HDG is enabled (see Appendix A for enabling or disabling NMEA 0183 sentences).
2. Transmit the Heading True (HDT) sentence using variation data from the Magnetic
Variation PGN (127258) from the NMEA 2000 interface if HDT is enabled (see
Appendix A for enabling or disabling NMEA 0183 sentences).
4.3 Variation Input via Manual Entry
If no other source of variation is available (i.e., from either the NMEA 0183 or NMEA 2000
®
interface), the SSC200 can be programmed with a fixed variation value for a given location
(this value can be found on most navigational charts). If variation is manually entered into the
SSC200, then it will do the following:
1. Transmit the Heading, Deviation & Variation (HDG) sentence including the variation
field as manually entered over the NMEA 0183 interface if HDG is enabled (see
Appendix A for enabling or disabling NMEA 0183 sentences).
2. Transmit the Heading True (HDT) sentence using variation data as manually entered
over the NMEA 0183 interface if HDT is enabled (see Appendix A for enabling or
disabling NMEA 0183 sentences).
3. Transmit over the NMEA 2000
®
interface the Magnetic Variation PGN (127258) with the
Variation Source field value corresponding to the manually entered variation. The
PGN’s Variation Source field will be transmitted with the lowest possible quality
indicator, which is “Manual Entry”.
WARNING: Magnetic variation changes as your position on the earth changes;
therefore, the variation should be adjusted with changes in position. The SSC200 will
not automatically adjust variation with changes in position; it is the responsibility of the
user to adjust variation with changes in position.