WeatherFax ...

[rgleason]

Originally Posted by WiggyBennett

rgleason

The background image on the installer has areas of white. Unfortunately, the text is also white and so invisible, some of the buttons are difficult to see. Suggest using a darker image.
The plugin defaults to disabled. Probably intended.
Leeway defaults to using a heel sensor. I doubt many people have one. I chose the manual heel input which I assume is based on the table.
I’ll have a proper play when we go sailing next (currently in Portugal getting ready for a passage to Madeira).

Thank you wiggybennett. When you get a chance can you upload a screenshot so we can see it? Probably best to upload to the Tactics thread here to keep things straight. Will be interested in your testing.



http://www.cruisersforum.com/forums/...in-166909.html

[BILLY_BUDD]

I have been having trouble importing weatherfax images from NOAA OPC ->Atlantic using the WeatherFax_pi plugin. Other sources seem to work OK though I haven's tested them all.

I am able to independently download a PNG and import/calibrate it "manually".

I have reinstalled Weatherfax_pi as a first course of action, the problem was not resolved.

I wondered if WeatherFaxInternetRetrieval.xml or CoordinateSets.xml might have a problem but I haven't been able to put my finger on a source file to replace them with. Assuming the reinstall does not over write them for me.

A screenshot of the fault notification received is attached for info. In the impage you can see that the plugin works for other stations as there is a synoptic chart from Boston in the background.

If the xml files are preserved on a reinstall is there a way to force a full over write of the plugin, without creating a new set of loose ends.

Any ideas, would be welcome! Chuck

[rgleason]

The weatherfaxinternetretrieval.xml is a moving target and needs updates ideally every 3 months. Please find the weatherfax MacOS thread where David Burch just updated this file. He has a link to download a new file.

[CarCode]

Originally Posted by rgleason

The weatherfaxinternetretrieval.xml is a moving target and needs updates ideally every 3 months. Please find the weatherfax MacOS thread where David Burch just updated this file. He has a link to download a new file.

Regarding his screenshot he is using Windows 10 however.

[rgleason]

Yes, true Carcode. However the file there does have more up to date url's.

I found his post here
https://www.cruisersforum.com/forums....php?p=3072802

[BILLY_BUDD]

I found the file from Mr. Burtch and when I finally got it copied into the right directory, problem solved. I didn't discover any OS/windows formatting issue either with the XML

You guys are great!

Sincerely, Chuck Wargo

[BILLY_BUDD]

Who Knows how you might embed a Geostrophic Wind Scale on a Weatherfax Synoptic Chart from NOAA OPC ->Atlantic. Some UK synoptic charts have such a scale embedded while NOAA chooses not to include such a detail. I find it useful when evaluating whether to stay put or move on for better protection under the threat of degrading weather.

[rgleason]

https://www.google.com/search?q=Geos...uxGRxCXqLEcieM

[rgleason]

RE Update of WxfaxInetRetrieval file, see David Burch


https://www.cruisersforum.com/forums...ml#post3072802

[DavidBurch]

I agree completely. We also need this to compare a model forecast such as GFS with the OPC or UK maps. In our book Modern Marine Weather ( https://www.starpath.com/catalog/books/1886.htm ) we have a table (2.4) that does this, but you can also do it with a formula:
Surface wind speed = 0.8 x 40 kts/(D x Sin Lat ), where D is the spacing of 4-mb isobars in units of degrees of Lat. The unusual format here is to stress that we use 0.8 and not the standard 0.6 or 0.7 for the frictional reduction seen in the typical geo wind diagrams. The book covers ways to find tune this for exceptional isobar curvature or air mass instability... keeping in mind that ±10% is optimistically the best we can hope for any formula, table, or diagram to work.

Originally Posted by BILLY_BUDD

Who Knows how you might embed a Geostrophic Wind Scale on a Weatherfax Synoptic Chart from NOAA OPC ->Atlantic. Some UK synoptic charts have such a scale embedded while NOAA chooses not to include such a detail. I find it useful when evaluating whether to stay put or move on for better protection under the threat of degrading weather.

[BILLY_BUDD]

Maybe we could toggle the measure function to read in knots using the formula when a weatherfax overlay is displayed. It would be more direct than trying to match the geostrophic wind scale to the charted Scale so that the measure tool could work like dividers in most examples one can find on the interweb.

That would help with transcription error and computational error.

[rgleason]

It is possible such a tool could be built for inside of weatherfax, but we need to get it programmed.

- Short Name of Tool: Geostropic Wind Scale is way too long.
- What formula?
- What units?
- What user adjustment in the calculation is needed, required?
- Operation: Pick tool 'GWS'? Pick start, Pick end, Show value
- Where to show the value?
- Maybe it would be easier to have the calcs built in somehow, so you hover between two lines and it determines the shortest distance at that point and shows the value?
Sort of like the grib files work when you hover.

[BILLY_BUDD]

Rick,

All good points. I will reach out to David Burch to see if he and I can agree to some code-able practical answers. He has some more experience to share I’m certain.

Chuck Wargo

For the moment the easiest answer “GWS” Geostrophic Wind Speed feels good.

More to follow. Chuck Wargo aka ‘Billy Budd’. Dave?????

[BILLY_BUDD]

I think the programming to find the inter-isobar distance automatically would be challenging because the isobars/weather fax are crude images. So best to let the human make the value judgement via mouse clicks.

The equation is a function of surface friction, Coriolis/latitude, pressure gradient ) I think those values have been reduced algebraically to the solution Davis Burch supplied. If we could see more of the proof, those details would reveal the dimensional analysis to confirm the inputs and result are all from the correct (same?) standard.

This reference info would also make an important contribution to the User Manual.

The ‘point eight’ looks like a surface roughness constar which might be a user preference....but besides possibly near shore, open ocean effects, I am unsure what the considerations may be.

I would favor temporary/ pseudo wind barbs as an output, ie a direction arrow with a scalar value for speed?

Let’s see what David Burch has to say.

[DavidBurch]

I started to answer these but it gets long fast and a bit hard to describe, so i will make a short video with a proposed tool, then come back with the link. Sounds like an interesting idea.

Originally Posted by rgleason

It is possible such a tool could be built for inside of weatherfax, but we need to get it programmed.

- Short Name of Tool: Geostropic Wind Scale is way too long.
- What formula?
- What units?
- What user adjustment in the calculation is needed, required?
- Operation: Pick tool 'GWS'? Pick start, Pick end, Show value
- Where to show the value?
- Maybe it would be easier to have the calcs built in somehow, so you hover between two lines and it determines the shortest distance at that point and shows the value?
Sort of like the grib files work when you hover.