I am not seeing True Wind Angle and Speed on OpenCPN

[J.Hernandez]

Originally Posted by barcoMeCasa

Great, getting somewhere!! So opencpn should see those as well if it is connected to tcp port 10110.

Bit out of my depth here but the code to create the VHW sentence has magnetic variation & heading as well, not sure but they might be needed??

keys: [
      'navigation.headingTrue',
      'navigation.magneticVariation',
      'navigation.speedThroughWater'

Do you have navigation.headingTrue & navigation.magneticVariation in the data browser as well?

Might be a red herring though....

Duh! I don't have HDG. If that is needed to display VHW then you have just solved the problem.

[barcoMeCasa]

Originally Posted by J.Hernandez

Duh! I don't have HDG. If that is needed to display VHW then you have just solved the problem.

Just asking the clever folks on discord to check if it is needed, not sure what timezone they are but shouldn't take too long for an answer..

[barcoMeCasa]

OK spoke to the author, yep , that's it. Needs those other 2 signalk values to work. There is a workaround but bit complex..
https://github.com/SignalK/signalk-s...eg-displayname

Way back at the start, what was it you wanted to do again? Was if record & play back on the VDR? Might be other ways to do something. Glad we got to the bottom of it though.

[J.Hernandez]

Originally Posted by barcoMeCasa

OK spoke to the author, yep , that's it. Needs those other 2 signalk values to work. There is a workaround but bit complex..
https://github.com/SignalK/signalk-s...eg-displayname

Way back at the start, what was it you wanted to do again? Was if record & play back on the VDR? Might be other ways to do something. Glad we got to the bottom of it though.

Well, thank you. That settles the issue. I may be looking into an IMU now.

[barcoMeCasa]

Originally Posted by J.Hernandez

Well, thank you. That settles the issue. I may be looking into an IMU now.

In the meantime just to see the VHW you could try pasting this into the data fiddler pane on the left & press send to server

[
  {
    "context": "vessels.self",
    "updates": [
      {
        "values": [
          {
            "path": "navigation.headingTrue",
            "value": 3
          }
        ]
      }
    ]
  }
]

also mag deviation if it isn't there >

[
  {
    "context": "vessels.self",
    "updates": [
      {
        "values": [
          {
            "path": "navigation.magneticVariation",
            "value": -0.191986
          }
        ]
      }
    ]
  }
]

that should create the missing signalk deltas temporarily and you can feel that at least it does work

[J.Hernandez]

Originally Posted by barcoMeCasa

In the meantime just to see the VHW you could try pasting this into the data fiddler pane on the left & press send to server

That worked!

What I did with the fiddler... Is it a permanent thing? Or it will just last for a few minutes?

[barcoMeCasa]

Originally Posted by J.Hernandez

That worked!

What I did with the fiddler... Is it a permanent thing? Or it will just last for a few minutes?

That signalk delta (a sentence is called a delta in sigk land) will stay until you reboot the signalk server. Glad it worked!!

Also, with your heading, I might be able to come up with something which would create a heading from GPS course over ground or just a default value if no gps COG so at least you can carry on for now.

Signalk might have a way to do it or node-red can do anything you can dream up.

Openplotter/signalk is actually not that hard to get going for a simple setup but it's immensely powerful under the hood

[J.Hernandez]

Yeah. I can see that. There's a lot of interesting stuff like Node Red, InfluxDB, grafana. But I have very little programming skills so it takes a while for me to assimilate this.

Thanks!

[CyKlop]

Originally Posted by Hakan

Using COG for true wind calculation will not make a usable true wind due to leeway or similar.

Actually, COG is exactly what you need along with heading. COG includes "leeway".

As others have said, the data needed is

1. Relative Wind
2. COG
3. SOG
4. Heading

From those you can calculate True Wind.

1. Rotate the relative wind direction by the Heading
2. Vector subtract the COG and SOG from step 1 to get True Wind

[J.Hernandez]

I've been reading about this and there appear to be two different schools of thought.

One recomends to calculate true wind from Apparent wind, COG, SOG and heading. The other to calculate from Apparent wind and STW.

I am not sure which way is most useful for my purposes. If what I ultimately want to do is get better data for racing, which one should I go with?

[CyKlop]

Originally Posted by J.Hernandez

I've been reading about this and there appear to be two different schools of thought.

One recomends to calculate true wind from Apparent wind, COG, SOG and heading. The other to calculate from Apparent wind and STW.

I am not sure which way is most useful for my purposes. If what I ultimately want to do is get better data for racing, which one should I go with?

STW then requires that you know what the direction of water movement is. Imagine you're in a 10 knot current pushing you sideways. Now you need to know the direction of water motion, your STW, your heading, the relative wind... a lot more complicated.

To calculate true wind, you need to know how your sensor is moving through the air and cancel that. COG/SOG gives that to you. STW doesn't.

[barcoMeCasa]

Originally Posted by J.Hernandez

I've been reading about this and there appear to be two different schools of thought.

One recomends to calculate true wind from Apparent wind, COG, SOG and heading. The other to calculate from Apparent wind and STW.

I am not sure which way is most useful for my purposes. If what I ultimately want to do is get better data for racing, which one should I go with?

Not a racer but i think if there's much tidal flow the racing guys like to know the wind referenced to the water more than over the ground so they know when to tack better. A lot of the time convention seems to call wind over the ground as ground wind and referenced to the water as true wind. If there's a couple of knots of tide flowing could make quite a difference.
The signalk derived data gives a few options >


https://www.npmjs.com/package/signalk-derived-data

True Wind Angle, Direction and Speed (based on speed through water, AWA and AWS)
True Wind Direction (based on AWA and headingTrue)
Ground Wind Angle and Speed (based on SOG, AWA and AWS)
Magnetic Wind Direction (based on AWA and headingMagnetic)
Magnetic Wind Direction (based on wind.directionTrue and magneticVariation)

[wholybee]

Originally Posted by J.Hernandez

I've been reading about this and there appear to be two different schools of thought.

One recomends to calculate true wind from Apparent wind, COG, SOG and heading. The other to calculate from Apparent wind and STW.

I am not sure which way is most useful for my purposes. If what I ultimately want to do is get better data for racing, which one should I go with?

For racing you want True Wind referenced to water. The reason is that you should be using your polars, and polars would be referenced to water.

[J.Hernandez]

Thank you! Very informative.

[barcoMeCasa]

I might be making it up..., not a racer...

Have you played around with the KIP dashboard? It's pretty powerful and good at displaying apparent & ground/true wind.

https://github.com/mxtommy/Kip

https://www.youtube.com/watch?v=uDas858rf6Y