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Navigation Functions

The Ockam system navigation functions are focused on aiding navigators and helmsmen for boat safety. They also provide vital inputs to other performance functions such as current calculation.


tells you where the boat is pointed but not necessarily where it’s going. Vital to navigation and helmsmnship, it is used by the system for dead reckoning, true wind and current.

  • Heading can be switched to Course Over Ground when needed (see Option 16).
  • There are 3 software settings (Options 17-19) to correct for lubber offset and semicircular errors (here’s a tutorial on compass adjustment).
  • The compass can also be the source for heel, pitch and turn rate.


is the position of the boat. Sounds like a function only a navigator could love, but in racing, marks are usually maintained by on-board software because they tend to be ‘floaters’, defined by where the true wind is blowing from. This software needs to have the current position in order to calculate their own waypoint range and bearing.

Waypoint Range & Bearing

This is the GPS output describing the next waypoint in its waypoint list. However, on-board software sometimes has a different value for this function.

Ockam provides a way for on-board software to override the GPS waypoint. When the software stops updating its waypoint, the system returns to the GPS output.

Back Range & Bearing

Back range and bearing refers to the last point the Reset Back R/B command was issued. The system maintains its own data on this point, independent of other hardware. This function is useful in prestart preparation.


is course and speed over ground.  By itself, this doesn’t seem to be useful, but, it is vital for computing current.


The Ockam system produces both surface and keel depth. When depth is input to the T1 processor, commands K15 and K16 set these parameters.


There are two logs, one of which is resettable.

Cross-track Error

is a report on how far off the rhumbline you are. It is a repeat of the GPS cross-track error (if provided).

Sea & Air Temperature

(tags ‘g’ and ‘g”) display one or two general purpose temperature values. The “Sea temperature” has a resolution of 0.1°C or about 0.2°F. Usually used to detect the gulf stream, and possible wind gradient conditions.

Barometer & Trend

(tags ‘G’ and ‘G”) display barometric pressure and pressure trend (the change in barometric pressure over the last hour).


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