Tidal arrow on Raymarine C80 not showing

[Gromski]

We've got the C80 and have turned on the various vectors in the options (wind, tide, COG, hdg) but only wind and COG are showing.

Do wind and heading need to have a compass attached to the plotter before they'll show up? Something like a flux-gate in an autopilot...?

Cheers

M

 

[trevorr]

I've had a C80 for a year or so now, and it wasn't until I upgraded the software on it last week that I realised that there were any Tidal arrows.

I'd just assumed that you needed to click on the little Tide box on screen and all you got was text. Now I get Green arrows on the screen.

You can download the software update from www.raymarine.co.uk

Trev

 

[Bloater]

The tidal arrow is derived from a calculation to show the difference between gps SOG and log speed, also the boats direction and COG needs to be taken into account to calculate the vector. Without a gps or heading sensor the plotter hasn't the info it needs to calculate the answer.

 

[Gromski]

TJR - are you talking about the tidal arrows that you can animate when you hover over the tidal diamonds on the chart? Those are currently working fine...

Quo - We've got GPS plugged into the plotter along with wind, speed and depth via seatalk.

 

[trevorr]

Yes I was, Wrong end of Stick again.

 

[Bloater]

Ah, but without knowing which direction the boat is pointing you do not have all the information needed to calculate the boat's vector.

The GPS gives you actual COG and SOG and therefore the first vector (relative to the satelite, or land) can be calculated.

The Fluxgate compass gives you the boat's course and the log/paddlewheel gives boat's speed, this gives you another vector (relative to the water you are moving through).

Subtract one vector from the other and you have calculated the effect of the tide.

Therefore without a fluxgate in the system you cannot have tide calculated. The fluxgate compass is included in an autopilot installation.