Specifications

AIRMAR

PB100 WeatherStation Technical Manual revision 1.007

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 bow of the vessel is pointing. COG refers to

the direction the vessel is traveling. While in an automobile 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:

The GPS receiver in the PB100 can calculate a position fix when it has achieved a

lock on at least three GPS satellites. If it has achieved a lock on four or more

satellites, the unit may be able to calculate a 3D position fix, meaning it can

determine latitude, longitude, and altitude. But if it has achieved a lock on only

three satellites, it may only be able to calculate a 2D position fix, meaning it can

determine latitude and longitude, but not altitude.

By default, the unit will automatically calculate a 3D position fix if it is able to,

but will fall back to 2D position fixing if there are not enough satellites being

tracked.

It is possible to restrict the operation of the GPS to only allow 3D position fixes

by sending the unit the command $PAMTC,OPTION,SET,2,2. If this is done,

then the unit will not calculate a position fix until it has achieved a lock on at least

four satellites.

Note that sometimes the GPS may be tracking at least four satellites, but is still

unable to calculate a position fix. This is because the positions of the satellites in

the sky must be satisfactory in order to achieve good geometry in the fix

calculation, as determined by the HDOP, VDOP, and PDOP values.