Pitch / roll / yaw data - how is it actually used by marine chartplotters etc.?

MattS

MattS

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My question about GPS satellite networks (GPS/GLONASS/GALILEO/BAIDOU - How important?) has led me to now be curious about the advantage of having pitch / roll / yaw data on a normal cruising sailing boat, and to wonder how that data is actually used if it's available on a NMEA network?

Is this data actually used by chartplotters etc. to make any practical difference to a normal cruising user?
 
MattS said:
My question about GPS satellite networks (GPS/GLONASS/GALILEO/BAIDOU - How important?) has led me to now be curious about the advantage of having pitch / roll / yaw data on a normal cruising sailing boat, and to wonder how that data is actually used if it's available on a NMEA network?

Is this data actually used by chartplotters etc. to make any practical difference to a normal cruising user?
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Main benefit is surely to the autopilot? The AI builds a pattern to predict what these variables do to the heading of the boat, and therefore how much pre-emptive rudder is applied. Just like when you're steering, an early firm correction is more effective than a later more drastic reaction; not only will you sail flatter and faster, but also more safely and with less power consumption.

Not sure what it does for the chart plotter.
 
I think the best answer has to be researched: I'll put Sea Dog on an outer mooring in Mersea Quarters where we have 15-20kts of East wind best on a spring tide. All you would need to do is to monitor the AP output (which should be constant I suppose) while you sit on the mooring for 12 hours while you monitor one or both of the plotters which doesn't have pitch and yaw and roll. I'll leave you on board with a bowl and towel. :). (Just a joke but it might be the most practical experiment)

Sorry, I just had to crack the joke!

Actually Gladys might chip in. When we are doing a survey, he steers and I issue instructions. I tell him I want a meridian -'turn to xxx' and he has to follow it. Now we won't know whether Gladys claims it is his steering or the AP and KA sensor! But we end up with a straight line of soundings.
 
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That makes sense - that it's more use for the AP than the chartplotter.

Given I'm tiller-steered, and use a tiller pilot, I can see that I will probably get limited benefit from having such data!
 
Unless you upgraded to an NKE, or similar high performance, sailing autopilot, then you won’t see any benefit. Most standard tillerpilots don’t have the functionality.
 
If you are just setting a heading, the tiller pilot will use the built in fluxgate I think, not the plotter. If, you are steering to a waypoint, the plotter will be taking into account the header from the KA plus other data so as to zero XTE. So I reckon the KA would be in action - provided that the plotter is getting and is accepting the Pilot lat/long as well as the header. I export the heading from the KA to the KM12. The lat/long from the KA is on the bus in the multiplexer but I don't ask the multiplexer to export that string to the KM12 - and I don't know that the KM12 would ignore its own sensor's lat/long - so I didn't bother to add that. I think as RJJ said, the heading is important. Any variation on lat/long would be so minimal that it would have no practical difference. But in bad conditions a true heading compared to the plotter sensor bobbing up and down could be the benefit.
 
I'd guess that you'd know if you had a fancy modern autopilot that supported all this data.

I believe the current models of Raymarine Evo ( £1000 - £2000) support it, but they usually come in a pack with the ACU control unit and the EV-1 accelerometer / gyro / compass bundled together, so you wouldn't need a 3rd party roll / yaw sensor. I would guess the budget B&G autopilot is similar.
 
No you're right - I have a Raymarine ST2000+ - so it can take NMEA or Seatalk for the purpose of following a waypoint, or sailing to the wind - but it's not clever enough to learn and compensate from pitch / roll data etc.
 
MattS said:
No you're right - I have a Raymarine ST2000+ - so it can take NMEA or Seatalk for the purpose of following a waypoint, or sailing to the wind - but it's not clever enough to learn and compensate from pitch / roll data etc.
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Your ST2000 like most other AP's only reads Sea State and learns from that. Basically YAW and the corrective action taken. After successive corrections - its learnt to reduce its amount of correction.

As to Plotter to AP .... AP steers based on its compass and sea state ... plotter detects positional wander and sends correction to AP ... nothing to do with Pitch / Roll / Yaw ... its purely CMG to make WP.
 
In your case no, there's no way to get the attitude (survey word for vessel movement pitch roll heave heading) into your plotter.

However,

Your GPS position data from advanced sensors like the simrad hs75 (which is Actully a hemisphere v200s with a sticker on it) can be significantly improved by use of internal processing. This is how the positional data is improved by attitude along with SBAS and enhanced correction services to the sub 10cm and 2cm accuracy.

Of course as navigators 5 odd meters of accuracy is perfectly good enough.

These advanced heading sensors work with simrad ac70 and nac 3 autopilots, furuno offer something similar. The evc 'brain' is built into the motion sensor itseflt so I Don thing raymarine support it. You don't need a seperate flux gate or compass with these GNSS sat compass systems.

But how much you would notice the difference between your 2-300 pound network gnss sensor and the 2500 pound one with an attitude sensor in it.... Well I doubt there would be any noticeable difference unless your recording multibeam sonar data!

The heading accuracy with these GNSS sensors is far better though down to about 0.5 degrees
 
I know nothing about this but from the link on your other thread, the gadget proclaimed a “9 axis” sensor, I wonder if this a marketing ploy and pitch and roll are completely irrelevant. I am guessing here but I wonder if the gadget comes with a pitch roll and yaw sensor built in (ie you can’t actually get a chip that only does yaw).

when doing ship dynamics at uni, there were only 3 axes, giving 6 degrees of freedom which covers our little 3D world. 9 axis sounds a bit over the top. Either something has changed in the last 30 years and they’ve found another dimension, these sensors were designed for the Tardis or the marketing department has been let loose without taking technicaL advice.
 
Our Raymarine EVO100 system installed two years ago comes with 9 axis unit, the data makes the autopilot work far better than the tiler pilot it replaced, especially in variable wind and bumpy waves with tides. Pitch and roll etc cum into play then
 
Many Inertial Measurement Units (IMUs) are typically marketed as 9 axis. 3 axis accelerometer (linear); 3-axis gyro (angular rate) and 3-axis compass, which is typically used to correct the gyro. It’s just some weird terminology that has become accepted and commonplace.
 
Scramp was designed round use of yaw etc to determine sea conditions and vessel stability. I think its described in the instructions and background - but Scramp is of only academic interest otherwise. If anyone finds a use for Scamp - I'm interested. There are a number of Apps deriving yaw etc, Accelerometer, vibsensor as well as Scramp. Most apps don't actually do anything with the data, except Scramp.

We have reached the point where our accuracy of positional data is factorially greater than the accuracy of our charts and it will be decades, if ever, that every rock is plotted to the accuracy of our 'gps et al'. This relates to position only, depth and tidal data (which is influenced by the weather) at the precise time necessary is simply another fudge. As someone mentioned earlier when you are able to achieve 0.5m accuracy - you can see whatever it is, unless a submerged rock - and then you just give it a wide berth ('wide' depends on when the survey was made - and in many places that was a long time ago). Around Tasmania we still have large patches of white - with the word 'Unsurveyed' reassuringly in large print.


I confess that I had no idea that yaw and pitch etc were available, easily, from a tablet (and a phone) and had I not had a an anchor fetish would never had known. We all pay for this facility and apart from making sure the screen is the right way round - 99.9% of the population will not care less. Another use is denying access to certain functions of your phone when you are driving. It has made me wonder what other data is measured and available (in our tablets, phone or 'chart plotter') of which we are unaware of - but pay for when we buy the device(s).. The big problem is if you ask 'can we measure yaw' someone will have the answer - when you don't know what to ask for and are simply inquisitive - you won't get an answer.

Jonathan
 
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If you play many of the new games on your iPad you will see the use of all the sensors that are built in, yaw, pitch, accelerometer etc. you control the game by moving the ipad around in free air
 
Daverw said:
If you play many of the new games on your iPad you will see the use of all the sensors that are built in, yaw, pitch, accelerometer etc. you control the game by moving the ipad around in free air
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each to their own :)

I'm fear I'm missing something important.......?

Jonathan
 
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MattS said:
My question about GPS satellite networks (GPS/GLONASS/GALILEO/BAIDOU - How important?) has led me to now be curious about the advantage of having pitch / roll / yaw data on a normal cruising sailing boat, and to wonder how that data is actually used if it's available on a NMEA network?

Is this data actually used by chart plotters etc. to make any practical difference to a normal cruising user?
Click to expand...
Where have you found this data . It is used on various ships and boats for specific purposes but would only appear on a navigators screen as information . Roll data will be used in the stabilising system which can also monitor pitch and yaw is a function used in the auto pilot system and may indicate that settings need tweeking .
 
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