ComNav Commander P2 - Correction Methods; Table 7 - NAV Mode Correction Methods

ComNav Commander P2 & P2VS Installation & Operation Basic Operations
Document PN 29010074 V4.1 - 132 -
Correction Methods
There are three different methods that the autopilot can use to process data from the
Navigation System, in order to update its Commanded Heading. Each has different effects
on the path that the boat follows.
You select which method you want the autopilot to use, by specifying “CTS”, “XTE” or “Both”
for the Correction parameter in the Nav menu.
The table below is a brief overview of the 3 methods. Full details on each method follow,
over the next several pages.
The data used in these methods is defined as follows:
• “Direction data” is the Bearing Origin To Destination (BOD) data in the NMEA
sentences from the Navigation System, or – if there is no BOD data – the boat’s initial
Heading at the time NAV mode is entered.
Note: the no-BOD condition for a whole route is possible only when the route is
straight to a destination – i.e., it has only the one destination waypoint. For
routes with multiple waypoints, the first leg can be with “initial Heading”, but
the Navigation System must provide BOD data for subsequent legs.
• “Steering data” is either the Course To Steer (CTS) data provided by the Navigation
System, or – if there is no CTS data – the Bearing Present To Destination (BPD)
data.
• The Cross-Track Error (XTE) data from the Navigation System, in Nautical Miles.
Setting Method Comments
CTS Course To Steer
The autopilot uses “steering data” only:
BPD CTS Heading or=
 Cross-Track Error is displayed, but not used.
XTE Cross-Track Error
The autopilot steers so as to minimize Cross-Track
Error as quickly as possible, using “direction” data:
(
)
(
)
NM/004XTEHeading BOD Heading °×+= or
 CTS/BPD data is not used, even if provided.
Both
Course To Steer
plus
Cross-Track Error
The autopilot steers so as to minimize Cross-Track
Error smoothly, using either “steering data” or “direction
data”, depending on what the Navigation System
provides:
 If CTS or BPD data is provided:
(
)
(
)
NM/360XTEBPD CTS Heading °×+= or
 If neither CTS nor BPD data is provided:
(
)
(
)
NM/004XTEHeading BOD Heading °×+= or .
Table 7 – NAV Mode Correction Methods