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Old 16-05-2018, 04:19   #1
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Plots Plugin

Dedicated to posts for the Plots_pi plugin.

This plugin has been renamed from Trimplot, and before that Sailtrim.
Old Thread: Chart Downloader/Updater Plugin
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Old 16-05-2018, 05:01   #2
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Re: Plots Plugin

Rick
I think the link to the old thread is pointing to something else.. not trimplot etc.

For giggles, I cloned and compiled the code from https://github.com/seandepagnier/plots_pi

First observation: It only uses the NMEA MWV sentence for wind. My system does provide VWR instead, so no luck with this plugin.

The tactics_pi works fine here, uses VWR, but does not do longer term plotting.

I would like to plot long term true wind direction and speed, for example to detect diurnal changes. The plot_pi also seems to store the data, so they are available after restarts of opencpn (good!). I guess I have to learn converting VWR to MWV with the nmea-converter plugin..


Dirk
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Old 16-05-2018, 05:18   #3
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Re: Plots Plugin

Quote:
Originally Posted by LeaseOnLife View Post
Rick
I think the link to the old thread is pointing to something else.. not trimplot etc.

For giggles, I cloned and compiled the code from https://github.com/seandepagnier/plots_pi

First observation: It only uses the NMEA MWV sentence for wind. My system does provide VWR instead, so no luck with this plugin.

The tactics_pi works fine here, uses VWR, but does not do longer term plotting.

I would like to plot long term true wind direction and speed, for example to detect diurnal changes. The plot_pi also seems to store the data, so they are available after restarts of opencpn (good!). I guess I have to learn converting VWR to MWV with the nmea-converter plugin..


Dirk
It would be easy to support VWR sentences, but I never heard of anyone using them. What sort of anenometer are you using?

Is there any different between MWV and VWR besides those three letters?
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Old 16-05-2018, 05:48   #4
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Re: Plots Plugin

Quote:
Originally Posted by boat_alexandra View Post
It would be easy to support VWR sentences, but I never heard of anyone using them. What sort of anenometer are you using?

Is there any different between MWV and VWR besides those three letters?

Hi Sean

my system is an older B&G Hydra 2000. It does output VWR as well as VWT. The VWT is not valid since my speed wheel doesn't work, and this system does not allow for using SOG for VWT calculation. Currently I rely on tactics_pi for true wind calculations, using SOG instead of STW.

MWV can be both, true and relative. I think it does 0-360 degrees only, while VWR is 0-180 from the bow, left or right.

see screenshot (currently at anchor) for VWT sentences:
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Old 16-05-2018, 05:54   #5
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Re: Plots Plugin

So, yes, VWR is quite different from MWV, MWV has one field for speed, while VWR can have three for knots, m/s and kph. in my case knots and m/s are filled, kph is not.

catb: NMEA Revealed MWV
catb: NMEA Revealed VWR
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Old 16-05-2018, 06:44   #6
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Re: Plots Plugin

in further talking to myself...

I think I am at a dead-end with the nmea-converter plugin. According to the wiki, observation by RythmDoctor

https://opencpn.org/wiki/dokuwiki/do...nmea_converter

Quote:
Note that VWR/VWT and MWV work totally differently: VWR provides wind angles from 0-180 with an additional parameter of L or R, while MWV provides wind angles from 0-359 with no L or R. Converting your obsolete VWR sentence to the more modern MWV sentence would seem to be impossible without a conditional if() statement, which appears to not be supported (since I was unable to get it to work).
Next? I probably should try node-red? Well, maybe I better wait for Sean to add VWR to the plot plugin.


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Old 16-05-2018, 11:11   #7
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Re: Plots Plugin

does it work correctly in the dashboard?
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Old 16-05-2018, 11:48   #8
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Re: Plots Plugin

Quote:
Originally Posted by boat_alexandra View Post
does it work correctly in the dashboard?

I don't use the dashboard much, since I use Tactics_pi. But I just tried and I get (valid?) numbers for
  • True HDG,
  • AWS,
  • AWA,
  • TWS
but

  • TWA (true wind angle) is empty,
  • TWD shows a number but as magnetic
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Old 16-05-2018, 17:56   #9
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Re: Plots Plugin

I tried implementing it now on github, but I don't know if it's going to work for sure.
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Old 17-05-2018, 05:33   #10
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Re: Plots Plugin

New pull from git: Doesn't work here yet. I attached a VDR file (remove pdf extension) with the sentences from my GPS and B&G system.

Since I don't have a working speedwheel, I filter out all true wind sentences from the B&G system (using kplex). Leftover valid sentences are:

GGA, RMC VTG, DBT, HDM, VWR (plus VHW for heading, see correction below)

With above tactics_pi works fine when forced to recalculate true wind based on SOG.


Cheers
Dirk


Correction:
In my efforts filtering, I filtered out VHW while opencpn was running, tactics_pi kept calculating TWA, TWD, TWS. But after a opencpn restart it didn't. So tactics_pi had kept some value (likely heading) from VHW to calculate true wind after I filtered it out.

I replaced the VDR-file, including the VHW sentence
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File Type: pdf VDR-LeaseOnLife.txt.pdf (6.6 KB, 4 views)
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Old 17-05-2018, 07:25   #11
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Re: Plots Plugin

I had a bug, try now
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Old 17-05-2018, 08:29   #12
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Re: Plots Plugin

Scratch what I said below... I was playing with node-red to create a XXMWV sentence, which then caused plot_pi to display TWS and TWA.


So no. without node-red faking messages, TWS and TWA are not displayed from VWR.


Dirk



Quote:
TWS and TWA work now, together with AWS and AWA.


one more please: can you get TWD to work with the limited data I have? Having TWA, heading and variation should be enough?


Thanks


Dirk
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Old 17-05-2018, 15:03   #13
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Re: Plots Plugin

Are you sure you tried with the latest git code? It parsed one of the sentences in your log without problem.
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Old 17-05-2018, 15:18   #14
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Re: Plots Plugin

Quote:
Originally Posted by boat_alexandra View Post
Are you sure you tried with the latest git code? It parsed one of the sentences in your log without problem.

It does! Something works.. look at the screenshot. To the far left, is when I fed data MWV R and MWV T, calculated via note-red (same data from the instruments) to Opencpn. To the right is the plot_pi calculating the same based on VWR. Once AWA goes left of bow, AWA calculation goes wrong, while TWA looks OK. Everything is fine when AWA is right of bow. I am at anchor, so TWA should be tracking AWA and TWS should be tracking TWA closely.


Dirk
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Old 17-05-2018, 17:06   #15
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Re: Plots Plugin

ok... now it's definately supposed to work
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