WeatherFax ...

[rgleason]

Yes It is intended to do wav files that are 16 bit, and I've done that before.
The Linux version has more direct control of the ssb and can obtain those wav files through the ssb as I understand it.

Windows users need another program to record the wav file, it's that correct?
Sean, are you saying windows users could initiate wxtoimg?

Sent from my SCH-I545 using Cruisers Sailing Forum mobile app

[rgleason]

Sorry if I misspoke or got it wrong.

Sent from my SCH-I545 using Cruisers Sailing Forum mobile app

[rgleason]

El Pinguino sent some weatherfax_pi JPEG and Wav files which are located in
Opencpn Beta File Thingie File Thingie 2.5.7
[rguser, rgpass] under wx-fax/El Pinquino

Hopefully Frank will be able to provide some more useful *.wav files for us to try with weatherfax. These files should work for windows users of the weatherfax_pi plugin.

He also referred to this Australian website
http://www.bom.gov.au/australia/charts/?ref=ftr
Which has such goodies as
http://www.bom.gov.au/australia/char...ptic_col.shtml
http://www.bom.gov.au/australia/char...forecast.shtml
http://www.bom.gov.au/australia/charts/4day_col.shtml

much of which is sent by SSB marine fax. Frank is going to send us some of these wav files for testing.

[rgleason]

Sean has created a rather comprehensive list of weather sources within weatherfax which remembers time and settings for each station.

To provide some visual reference on Opencpn charting, there are Worldwide Marine Weather Stations available as a layer, under Using OpenCPN for Odds and Ends created by PjotrC http://www.cruisersforum.com/forums/...ml#post1435908

Each of the Weather Station waypoints has a link to the respective website.

It might be useful for those using Weatherfax_pi

[rgleason]

Regarding the wav file in Opencpn Beta File Thingie wx-fax/El Pinguino named 12270348.wav. This file does load using Opencpn3.3.1303 and the most current Weatherfax_pi (MSCV++ compile with Opencpn v3.3.1117) on Opencpn Beta File Thingie. However the way I have applied the coords, it appears to be Conical which is not supported.

I was able to load and display in Opencpn, the sound or WAV file "2001-06-21-09-00-GYA-11086.wav" also located in Opencpn Beta File thingie same directory tree. This file appears to be a different type of projection than polar, or I did not select the coords properly, however it is a WAV file that was read and did display as an overlay on the chart. See attached.

Perhaps Frank has gotten this far using WAV files, I do not recall if I had successfully read WAV, with the plugin, but it looks like this will work, provided we get the right files and coordinates.

[El Pinguino]

In Australia at least all the wefax products are conical projection except the tropical ones which are mercator.
I received a good asian msl from Charleville yesterday but it is 50mb so I will have to do something with it before sending,
cheers,
El Ping

[rgleason]

El Pinguino, perhaps Sean or someone else would be able to program "conical projection" at some point, if it would help. The reason seems pretty good. I'd enter a feature request on Tracker under Weatherfax_pi project if you could use it.

[seandepagnier]

Originally Posted by rgleason

Regarding the wav file in Opencpn Beta File Thingie wx-fax/El Pinguino named 12270348.wav. This file does load using Opencpn3.3.1303 and the most current Weatherfax_pi (MSCV++ compile with Opencpn v3.3.1117) on Opencpn Beta File Thingie. However the way I have applied the coords, it appears to be Conical which is not supported.

I was able to load and display in Opencpn, the sound or WAV file "2001-06-21-09-00-GYA-11086.wav" also located in Opencpn Beta File thingie same directory tree. This file appears to be a different type of projection than polar, or I did not select the coords properly, however it is a WAV file that was read and did display as an overlay on the chart. See attached.

Perhaps Frank has gotten this far using WAV files, I do not recall if I had successfully read WAV, with the plugin, but it looks like this will work, provided we get the right files and coordinates.

Conical _is_ supported, but you cannot compute the parameters, must manually and visually align it. This is because polar and mercator are really special cases of conical.

Anyway... to support conical like polar would take a lot of effort.. it took 3 days to implement the polar code.. so look at the math code.. it's a bit ugly.

The new version in git should support capture using portaudio.. so this could potentially work in windows, but I don't know. Unfortuantely it seems to drop data with high cpu usage in linux and I am not really sure why yet.

[rgleason]

Thank you Sean, for explaining about Conical support.

We're going to try to work up to Windows "capture using portaudio", but first I'll try it with Linux. Need to find a radio to connect to...

[seandepagnier]

If you have no radio, you can plug output to input and play a recorded file.

[El Pinguino]

Originally Posted by boat_alexandra

If you have no radio, you can plug output to input and play a recorded file.

You can do better than that.... download VB-Audio Cable here... VB-Audio Virtual Cable

That program is also excellent when using an FCD or any other SDR to download WxSats , Wefax etc...

El Ping

[Littlechay]

Originally Posted by rgleason

El Pinguino, perhaps Sean or someone else would be able to program "conical projection" at some point, if it would help. The reason seems pretty good. I'd enter a feature request on Tracker under Weatherfax_pi project if you could use it.

You could be barking up the wrong tree in trying to make images from polar orbiters fit a projection. They don't transmit a formatted image but a continuous fax tone of what they are seeing in a swathe about 3000km wide. They are just continuously scanning their suborbital point. I don't know the technicalities of overlaying the image to a map or vice versa, but knowing that the image width and orbital track must help.. what is probably needed is for the plugin to understand Keplarian elements so that it can calculate the orbital path.

See (wikipedia article) and (NOAA polar data users guide)

[rgleason]

Littlechay, I think you may have a good point about using the overlay features in weatherfax. With SAT [I mean APT] are the images always unique depending on when you receive the satellite signals? Or does the satellite take shot at the same point in space on each orbit and then start transmitting that image? I know little about how this works.

Frank [El Pinguino] will probably have some insight into this too. By the way Frank, have you tried Sean's other plugin rtlsdr.dll??

Here is how it started and why. http://www.cruisersforum.com/forums/...ml#post1224421

Here is the current version: http://www.cruisersforum.com/forums/...ml#post1441639

It loads and appears to work in windows isofar as the menus go, but I don't have equipment to test it yet. I am sure Sean would appreciate some feedback.

[rgleason]

From the Wiki APT under

Images "The images are corrected for nearly constant geometric resolution prior to being broadcast, as such the images are free of distortion caused by the curvature of the Earth."

Synchronization and telemetry: The synchronization information, transmitted at the start of each video channel, allows the receiving software to align its sampling with the baud rate of the signal, which can vary slightly over time

Receiving:
An APT signal is continuously broadcast, with reception beginning at the start of the next line when the receiver is within radio range. Images can be received in real-time by relatively unsophisticated, inexpensive receivers during the time the satellite is within radio range, which typically lasts 8 to 15 minutes.

Broadcast Signal:
The signal itself is a 256-level amplitude modulated 2400Hz subcarrier, which is then frequency modulated onto the 137 MHz-band RF carrier. Maximum subcarrier modulation is 87% (±5%), and overall RF bandwidth is 34 kHz. On NOAA POES vehicles, the signal is broadcast at approximately 40dBm (10 watts) effective radiated power.

[Littlechay]

Originally Posted by rgleason

With SAT [I mean APT] are the images always unique depending on when you receive the satellite signals?

Yes always unique. There is no "shot" as such the satellite is continuously sending line by line what it sees underneath itself. So if the satellite passes directly overhead you'll be able to receive images that cover a good 1000 - 1500+ miles north and south of your location. I don't have my station up and running right now but hopefully in a few weeks time I can provide some samples.

There is a lot of information available in the images the can be extracted by quite sophisticated software. I think this is definitely a case where OCPN should probably not try to reinvent the wheel. If images from other sources, Wx2IMG for example, can be imported then great, but decoding directly into OCPN would require a great effort to produce all the information that a dedicated programme delivers.

I find the satellite images really useful on ocean passages. At least in the higher latitudes you can see the positions of fronts, and confirm the weather patterns shown on the GRIBS. The height of the cloud tops can be measured (on the IR images by measuring temperature); this along with physical area, barometric pressure etc. can give you a good insight into whether or not the GRIBs are telling the truth. Big thunder storms are also pretty easy to spot.