B&G Deckman - Manual (Page 120)

NMEA Instrument System
7.15
NMEA Instrument System
The way in which Deckman handles instruments which offer the NMEA
interface is different from either the Hercules or the Ockam system. The
most important difference for you is that Deckman cannot write back to
the instrument system so that Deckman information can be shown on the
instrument displays, nor can you calibrate the instrument system from
Deckman; these are facilities offered by the B&G and Ockam
proprietary interfaces but not the NMEA standard.
The other difference is that Deckman calculates all of the wind
information from the basic variables apparent wind angle and speed,
boat speed, and heading. To get the best calibration Deckman allows
you to specify a maximum angle of heel so that it can calculate an
expected angle of heel and an expected leeway, and also correct the
apparent wind angle for the heel error.
The two diagrams in Figure 7.9 show how the maximum angle of heel is
reduced as a function of the apparent wind speed and apparent wind
angle. Although the function will not quite reach zero at 180 degrees the
angle is small enough for the effects to be negligible.
Figure 7.9