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Old 18-03-2020, 14:26   #1321
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Re: WeatherFax ...

Hereís an example of a output from an iOS app (Windy). Itís too cluttered for our purposes, but the core info is not bad 1 line, wind speed and direction. Simple because the underlying info supplied by the navigation chart is important to us. Click on the image to display....

Click image for larger version

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Old 18-03-2020, 15:08   #1322
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Re: WeatherFax ...

Here is a video with a few notes on this idea. https://youtu.be/XBOFrmYvUdE

As for the display, i would recommend numbers for the wind direction, ie 315 rather than NW.

We also see in the video that OpenCPN grib viewer has wind barb feathers on the wrong side. The ones shown are for southern hemisphere. Granted this is a strange convention, but likely worth following since met agencies around the world use it. Namely back to the wind, feathers are on the low pressure side... i also know of a few navigators that use the concept in reading weather maps.
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Old 18-03-2020, 16:50   #1323
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Re: WeatherFax ...

David! An excellent demo of the possibilities.....Chuck Wargo
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Old 18-03-2020, 17:52   #1324
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Re: WeatherFax ...

Maybe we can train AI to interpret weatherfax images and the AI could redraw the map making corrections...

This is basically outside the scope of the plugin.
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Old 19-03-2020, 16:49   #1325
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Re: WeatherFax ...

Well apparently Sean doesn’t feel this idea has much utility, or if it does, he doesn’t feel it is appropriate for Weatherfax. It does overlap GRIB strategies, but is more data frugal. (I think the video errantly inferred an entire grib vector field might be generated in this manner, though I am fairly certain that was not the point)

Sean has done great work with Weatherfax to his credit.

As an aside, I’ve used it very successfully to overlay USACE hydrographic surveys (Fathometry) of ICW and many class 1 and lesser inlets to great advantage from a piloting perspective. Thank You. Sean

But, that begs the question. Where to from here? Drop it, or discus the merits of the method in a should OpenCPN or shouldn’t it and should we continue with the definition? I’ve some opinions but prefer to hear from others.

Doesn’t OpenCPN user community to accomplish this by way of crowd endorsement? The idea could easily die on the vine there as well in that deliberative process.

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Old 19-03-2020, 17:18   #1326
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Re: WeatherFax ...

I have to say that i agree with Sean. I think this can be done manually just fine.

My response was to answer the question if it were to be done, what
might it look like, and to indeed answer specific questions presented to me. I was not proposing the function myself.

You are right about the grib background. This procedure is something that is used in reading a graphic weather map. Nothing to do with gribs, other than we can use the gribs to test the formula. Again, it is a crucial skill to have, but easily done by hand without an app or plugin.

I can change the title of the video and leave it as a demo of how to do this... or just make a new one.

As far as what happens to the idea, we might keep in mind that we can always do just what was done in the video, namely load the model grib on top of the map we want to read, analysis or forecast, and that way see what the winds are supposed to be. The only time we really need this manual analysis is when we do not have model data, or we have a case where the isobars of the models do not agree with the maps. In such a case we would defer to the maps, and then need to figure the winds. The table in our book solves this very well without calculations.

Getting the wind feathers on the conventional side of the barbs in another issue, and i would recommend fixing that.... meaning put it on a list for when the hood is open the next time. Probably not worth a lot of extra work on its own.



Quote:
Originally Posted by BILLY_BUDD View Post
Well apparently Sean doesnít feel this idea has much utility, or if it does, he doesnít feel it is appropriate for Weatherfax. It does overlap GRIB strategies, but is more data frugal. (I think the video errantly inferred an entire grib vector field might be generated in this manner, though I am fairly certain that was not the point)

Sean has done great work with Weatherfax to his credit.

As an aside, Iíve used it very successfully to overlay USACE hydrographic surveys (Fathometry) of ICW and many class 1 and lesser inlets to great advantage from a piloting Thank You. Sean

But, that begs the question. Where to from here? Drop it, or discus the merits of the method in a should OpenCPN or shouldnít it and should we continue with the definition? Iíve some opinions but prefer to hear from others.

Doesnít OpenCPN user community accomplish this by way of crowd endorsement? The idea could easily die on the vine there as well in that deliberative process.

Comments?
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Old 19-03-2020, 18:38   #1327
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Re: WeatherFax ...

Quote:
Originally Posted by boat_alexandra View Post
Maybe we can train AI to interpret weatherfax images and the AI could redraw the map making corrections...

This is basically outside the scope of the plugin.

Sean is absolutely right about this. It can be totally independent. What is needed is a way of adopting a drawing/measuring tool to also calculate a value and show it.


That could be a very simple plugin or it could be included with ocpn_draw for example. I kind of think the first option is better.
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Old 21-03-2020, 03:36   #1328
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Re: WeatherFax ...

Quote:
Originally Posted by rgleason View Post
Sean is absolutely right about this. It can be totally independent. What is needed is a way of adopting a drawing/measuring tool to also calculate a value and show it.


That could be a very simple plugin or it could be included with ocpn_draw for example. I kind of think the first option is better.
I agree, a simple additional menu option to the measurement tool whenever the weatherfax-pi is activated would be a valuable tool. No need to draw feather or the like - just a simple dialog showing the numbers.
My2cent -
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Old 21-03-2020, 05:32   #1329
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Re: WeatherFax ...

Quote:
Originally Posted by skipperearly View Post
I agree, a simple additional menu option to the measurement tool whenever the weatherfax-pi is activated would be a valuable tool. No need to draw feather or the like - just a simple dialog showing the numbers.
My2cent

I don't believe this will ever be code inside of OpenCPN, the main program, because it is too ancillary. Therefore the code for the "Measurement" tool will have to be copied and made into a very small plugin, which then gets tested and perhaps after awhile gets incorporated into weatherfax as a second icon.


Now you need to find a volunteer programmer to do this. It is a useful, simple project.
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Old 26-03-2020, 10:57   #1330
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Re: WeatherFax ...

Roger on the Programmer.

Is there a process? Maybe a OpenCPN programmer society....please excuse my naivete'. Maybe a more generic thread I could post to? This thread might not have enough visibility to gain the necessary programmer bandwidth....
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Old 26-03-2020, 12:53   #1331
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Re: WeatherFax ...

Billy_Budd ...

Probably not the right person to respond but I did study the video of what was needed. The measurement tool part is easy but the challenge is the wind direction. Calculation of the angle could quickly become complicated. Do we allow 10 degrees for friction? At what latitude? Open-water?

While downloading a weatherfax is it more sensible to download a grib file at the same time?

Mike
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Old 26-03-2020, 23:05   #1332
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Re: WeatherFax ...

Quote:
Originally Posted by Rasbats View Post
Billy_Budd ...

Probably not the right person to respond but I did study the video of what was needed. The measurement tool part is easy but the challenge is the wind direction. Calculation of the angle could quickly become complicated. Do we allow 10 degrees for friction? At what latitude? Open-water?

While downloading a weatherfax is it more sensible to download a grib file at the same time?

Mike
Agree that this part would be quite complicated as the plugin won't know the flow direction of the isobars. So would require two lines to be drawn; one along the isobars and the perpendicular measurement. It could of course assume that the user has drawn the measurement line perpendicular.

One point. The fax could well be received by radio by somebody with no way to download GRIBs. And I suspect this may have been the point of the OP...

Personally I am happy to look at a weather chart and eyeball it for windspeed and direction.
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Old 27-03-2020, 03:20   #1333
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Re: WeatherFax ...

Billy Budd are you at Ft Racheal Marina, Mystic?
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Old 27-03-2020, 04:23   #1334
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Re: WeatherFax ...

Rick,

I am at Boating on the Thames...up the Thames River...abeam of the Nautilus Museum, just north of Connecticut College...
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Old 27-03-2020, 09:03   #1335
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Re: WeatherFax ...

Does this help? The flows are directional...so measure into low pressure and out of high pressure....and derive you hemisphere from you position....
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