What is “Heave” on my Raymarine system?

[benzy]

Installed a new Raymarine autopliot and instrument pack. Playing with the i70s screen (which is fun!) and looking at all the different data points I can display.

There are a bunch under “Boat” such as Pitch, Roll, etc that are no doubt coming from the EV-1 sensor core in the autopilot system.

However, there is one in there called “Heave” which is measured in metres. What is this exactly? Can’t find any reference in the manual.

My guess, it’s the amount the boat is moving up and down due to swell, and used depth sensor to calculate. Am I right?

Cheers

[StuM]

You are correct in your first supposition, but your second one is doubtful.

A vessel has axial motion (ie rotation) in three directions, pitch(front to rear), roll (side to side) and yaw(turn to port/starboard).

It also has translational motion (i.e. linear movement) in three directions heave(up and down), surge(forwards and backwards) and sway( sideways).

Systems may use GPS, depth sensor, accelerometer or a combination of these methods to determine heave.


The EV-1 has a 3-axis digital accelerometer as well as 3-axis digital compass and 3-axis gyro digital angular rate sensor, so I would expect it to be using the accelerometer.

[benzy]

Thanks Stu

I am getting a “- - -“ reading for Heave at the moment. I am in deep water (ie no depth reading) which is why I thought it might use the depth sensor. Will see if I get a heave reading once back in shallower water

[weavis]

I think the Australian Ray marine software word is chunder....

[StuM]

Originally Posted by weavis

I think the Australian Ray marine software word is chunder....

That's the Bruce marine word

https://www.youtube.com/watch?v=bNBy1D1Y0h4

[weavis]

I had forgot that sketch...........still as fresh as the day it was filmed.

[jonarck]

And here I thought that it was the result of eating too much ho...and cleaning-up of the Raymarine system would be required...

[benzy]

Well, been sailing around in shallower waters and my heave reading is still “- - -“ so it doesn’t appear to come from the depth sounder or the EV-1.

Surely it doesn’t need gps? I wouldn’t think gps had the accuracy for this?

[Tommo]

Resurrecting a very old thread here, but this is the only reference on the internet I can find to Raymarine "heave" figure.

Like the OP my i70 shows three dashes permanently. The ACU100/EV1 seems to be working ok in limited calm water testing so far. But since the system is still under warranty I would rather have it fixed (if broken) before I find out later that there is a so far hidden fault.

So does anybody get figures other than three dashes on their system?

[SkipD]

Nice visual on the topic

[Tommo]

OK, maybe I should have started a new thread….

I know the definition of heave.

My question is why is my Raymarine system showing three dashes?

Does three dashes indicate a fault? My autopilot seems to work ok in limited testing so far, but I would prefer to know if it is faulty before taking it into seas where there is a lot of “heave”

[donradcliffe]

The answer to your question can be found in the word "Raymarine". The farmers who do the programming for Raymarine don't have an algorithm in their autopilot software which uses the heave data, so they ignore it.

[capt jgw]

Originally Posted by donradcliffe

The answer to your question can be found in the word "Raymarine". The farmers who do the programming for Raymarine don't have an algorithm in their autopilot software which uses the heave data, so they ignore it.

It probably needs extra sensors to make it work, but I don't know what those might be. Can't think of a reason it would be helpful on our sized boats anyway. On a big ship, maybe it would be. The autopilot is two dimensional so it doesn't care.

[Tommo]

I got a reply from Raymarine support and you are correct - the Raymarine autopilots (which I have) don't measure heave. I guess the i70 display incorporates the possibility to view heave data in case it is connected to a more advanced autopilot that does measure and use heave.

[stevead]

Depending on whether you trust manufacturer's product documentation, the Raymarine EV-1/EV-2/ACU Installation manual indicates the EV-1 does not transmit nor receive the NMEA 2000 PGN 127252 (Heave).

You could have possibly avoided a lot of angst by reading the manual.