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16-05-2018, 05:01
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#2
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Registered User
Join Date: Apr 2008
Location: out cruising again, currently in Fiji
Boat: Sailboat
Posts: 1,466
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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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16-05-2018, 05:18
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#3
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Registered User
Join Date: Aug 2009
Location: oriental
Boat: crowther trimaran 33
Posts: 4,414
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Re: Plots Plugin
Quote:
Originally Posted by LeaseOnLife
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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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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16-05-2018, 05:48
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#4
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Registered User
Join Date: Apr 2008
Location: out cruising again, currently in Fiji
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Posts: 1,466
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Re: Plots Plugin
Quote:
Originally Posted by boat_alexandra
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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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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16-05-2018, 05:54
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#5
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Registered User
Join Date: Apr 2008
Location: out cruising again, currently in Fiji
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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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16-05-2018, 06:44
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#6
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Registered User
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Location: out cruising again, currently in Fiji
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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).
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Next? I probably should try node-red? Well, maybe I better wait for Sean to add VWR to the plot plugin.
Dirk
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16-05-2018, 11:11
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#7
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Registered User
Join Date: Aug 2009
Location: oriental
Boat: crowther trimaran 33
Posts: 4,414
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Re: Plots Plugin
does it work correctly in the dashboard?
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16-05-2018, 11:48
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#8
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Registered User
Join Date: Apr 2008
Location: out cruising again, currently in Fiji
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Re: Plots Plugin
Quote:
Originally Posted by boat_alexandra
does it work correctly in the dashboard?
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I don't use the dashboard much, since I use Tactics_pi. But I just tried and I get (valid?) numbers for
but
- TWA (true wind angle) is empty,
- TWD shows a number but as magnetic
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16-05-2018, 17:56
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#9
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Registered User
Join Date: Aug 2009
Location: oriental
Boat: crowther trimaran 33
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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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17-05-2018, 05:33
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#10
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Registered User
Join Date: Apr 2008
Location: out cruising again, currently in Fiji
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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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17-05-2018, 07:25
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#11
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Registered User
Join Date: Aug 2009
Location: oriental
Boat: crowther trimaran 33
Posts: 4,414
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Re: Plots Plugin
I had a bug, try now
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17-05-2018, 08:29
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#12
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Registered User
Join Date: Apr 2008
Location: out cruising again, currently in Fiji
Boat: Sailboat
Posts: 1,466
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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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17-05-2018, 15:03
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#13
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Registered User
Join Date: Aug 2009
Location: oriental
Boat: crowther trimaran 33
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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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17-05-2018, 15:18
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#14
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Registered User
Join Date: Apr 2008
Location: out cruising again, currently in Fiji
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Posts: 1,466
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Re: Plots Plugin
Quote:
Originally Posted by boat_alexandra
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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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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17-05-2018, 17:06
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#15
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Registered User
Join Date: Aug 2009
Location: oriental
Boat: crowther trimaran 33
Posts: 4,414
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Re: Plots Plugin
ok... now it's definately supposed to work
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