Tidal stream compensation – Raymarine autopilot + ST4000+ User Manual
Page 38
Chapter 3: Advanced Operation
23
3
If the cross track error is greater than 0.3 nm, the ST4000+ will sound
the Large Cross Track Error alarm and shows whether you are to the
port (Pt) or starboard (Stb) of the planned track.
To cancel the Large Cross Track Error alarm:
•
press standby to return to hand steering, or
•
press auto to return to Auto mode and retain the current heading
Note: When the Large Cross Track Error alarm sounds, it usually
means that the cross tide is too great for your boat’s current speed.
Tidal stream compensation
Under most conditions, Track mode will hold the selected track to
within ±0.05 nm (300 ft) or better.The autopilot takes account of the
boat’s speed when computing course changes to ensure optimum
performance over a wide range of boat speeds. In order of preference,
the ST4000+ uses:
•
measured boat speed (speed through water)
•
if this is not available, it uses the speed over ground (SOG)
•
if this is not available, it uses the cruise speed specified in Dealer
setup (see page 112)
D3261-2
Waypoint 2
Waypoint 1
Tidal component
Boat's speed through w
ater
Boat's speed over ground