Airmar LB150 - Manual (Page 61)

LB150 WeatherStation Technical Manual revision 0.013
Proprietary and Confidential
PRELIMINARY - DRAFT 58
Option 5:
<3> 5 = Enable Type 0 Messages
<4> 0 = Ignore Type 0 messages for 60 seconds
1-39 = Enable Type 0 messages as data
255 = Ignore Type 0 messages (default)
Notes
Option 1:
If the local magnetic inclination (dip) is severe, this can produce errors in the
compass heading when the vehicle is not level. Since the compass heading is
used in the calculations for true wind, this can also result in errors in the reported
true wind speed and direction. (Apparent wind is not affected.) This option is not
applicable to stationary instruments.
The WeatherStation can be instructed to use Course Over Ground (COG)
provided by the internal GPS in place of the internal compass heading in the
calculations for true wind. The command to enable this feature is
$PAMTC,OPTION,SET,1,1. If this feature is enabled, then the COG will be used
instead of internal compass heading for calculation of true wind only if the GPS
has achieved a fix, and if the Speed Over Ground (SOG) is greater than 3 knots.
If there is no GPS fix, or if the SOG is 3 knots or less, then the internal compass
heading will be used.
Do be aware when using this feature that Heading and COG are not the same.
Heading refers to the direction the front of the vehicle is pointing. COG refers to
the direction the vehicle is traveling. While in an vehicle these values are likely
to be nearly identical, in a boat they can differ because of the effects of wind and
current on the vessel. The rationale for using COG instead of heading in the
calculations for true wind is that the difference between COG and actual heading
might be less than the error in the reported compass heading due to dip.
The setting is saved in nonvolatile EEPROM within the WeatherStation.
To disable this feature, use the command $PAMTC,OPTION,SET,1,0. When
disabled, the COG will not be used in place of internal compass heading under
any circumstances.
The WeatherStation may be queried to determine the state of this feature. If the
command $PAMTC,OPTION,Q,1 is received, the unit will transmit the reply
$PAMTR,OPTION,1,0 if the feature is disabled, or $PAMTR,OPTION,1,1 if
enabled.
Option 2: