STW vs SOG for Evolution Autopilot Speed Input

[Chuck - Raymarine - Moderator]

STW vs SOG for Evolution Autopilot Speed Input

Evolution autopilots are dependent upon speed data to maximize the performance of the autopilot. Under conditions of leeway (current and wind), autopilot performance will be maximized when the autopilot has been interfaced to a source of accurate speed through water data. This is particularly so for slow moving vessels such as vessels having displacement hulls or vessels operating at trolling speeds. In the absence of a source of accurate speed through water data, the autopilot will automatically choose GPS SOG as its speed input when either of following two conditions occur:
- the autopilot has not been interfaced to a source of speed through water data
- the autopilot has detected a malfunctioning or poorly calibrated source of speed through water data.
Should neither of the above conditions be detected, then the system will automatically choose speed through water as the speed input.

The operator may also manually select the autopilot's Speed Input (MENU->SET-UP->AUTOPILOT CALIBRATION->VESSEL SETTINGS->SPEED INPUT) should the AUTO setting not be yielding satisfactory performance. The Speed Input setting will not be available if the Calibration Lock feature (MENU->SET-UP->AUTOPILOT CALIBRATION->COMMISSIONING->VESSEL SETTINGS->CALIBRATION LOCK) has been enabled. The most common indicator of an Evolution autopilot responding to poor speed data input would be significant S-ing of increasing magnitude when the autopilot has been commanded into Auto (locked heading) mode. Please click here to view a FAQ addressing this subject.


RAYFAQ#