Open CPN, GRIB files, and IridiumGO!

[SV Mighty Quinn]

Hello all.
I have been searching around, and cant seem to find a solution. Maybe someone else has sorted this??

I am looking for a way to download GRIB files with an IridiumGO! and view them on my tablet.

I am using a Galaxy A8 with Android version 13, and the paid version of OpenCPN.

When I am connected to the Iridium GO! and request a new GRIB file download, I receive the error message 'download failed please check logs'. This does not happen when I am connected to high speed internet.

I am also experimenting with SailGrib which will send a generated request directly to the IridiumMail spool. Is this possible in the OpenCPN app?

Is there a setting that will allow me to change how the request is sent? Or alternatively, as in the desktop version of OpenCPN, copy/paste a generated request that I can send through the Iridium mail app?

Thank you for reading.

[rgleason]

Obviously, as a workaround, if you can receive and download the grib in any way, you can load it under OpenCPN using grib_pi. So what does the log say?
Perhaps upload it to here.

[svmobert]

It fails because the Iridium Go is not an open connection to the Internet (though a Go! Exec can do that). Any software trying to make a data connection through a Go! needs to be able to communicate with the Go's API to request that the Go! make a connection, after which the software can send/receive data, and then once complete, tell the Go! to disconnect. This is what Iridium Mail, Xgate, OCENSMail, OneMail, PredictWind Offshore, etc all handle.

It sounds like the OpenCPN for Android app doesn't have a GRIB email requestor, in which case copy/paste isn't really possible.

You might try using a different grib requestor app to request and retrieve the gribs, then open those files in OpenCPN if the Android app supports that.

Alternatively, you can try the following, but it may not work...

In the Iridium Mail app, there is a make connection feature where you can tel the Go! to connect and just stay connected for a period of time.. You could try to use that to start a connection, then have the OpenCPN app request the GRIB file, then end the connection when you are done. Depending on what servers and ports the app uses to download GRIBs from, it's possible it may be blocked without modifying the Go!'s firewall as well.

Further, depending on the size of the GRIB's the app downloads (typically determined by the size of the area you are getting weather for, number if days, intervals per day, resolution of the data, and which data points you are requesting), the downloads may or may not be successful. Ie: if the file is 1MB in size, it will take an hour or more to download and very likely the connection will drop in the middle, and if the app doesn't support checkpoint-restart (which it wouldn't need for broadband connections) then it will never succeed.

All of these things are why PredictWind Offshore, and other Go! certified apps are on the market, because they know how to make a connection through the Go! and know how to handle the slow connection.

Unless the OpenCPN developers get into the Iridium Developer community, access the SDK and use that SDK to add Go! functionality to the app, and also implement safeguards for the slow connection such as file size limits and/or checkpoint restart, it won't work or work well.

I searched a bit about email requests for the Android OpenCPN app and it seems it does not do that, based on some of the results I got.

[rgleason]

Very interesting. Thank you for posting, Richard. I doubt the opensource community is going to use the Go API, Elon and all. Regarding file size which could very well be an issue, I suggest using "walking gribs" which is supported by grib_pi, to reduce the file sizes. Not many people know about that or use it.


Really Predictwind has the right approach for Go, by just sending results and computing on the server.

[SV Mighty Quinn]

Thanks for all the detailed information, that is very interesting.

Ill give walking gribs a try

The Iridium connection is expensive enough, without a secondary subscription.

[RonaldL]

You can send emails through email app, can't you?
Than use saildocs.com emailing.
Save the grib to your device.
Open in opencpn.
Grib's do not have to bigger than 2 kb.
I used saildocs during my circumnav all the time.

[SV Mighty Quinn]

yes, I know how to do this. Was just playing with the Android app and wondering if there was something I was missing there, as the desktop version will generate the grib request for email.

Doing it manually works easy enough, but drawing a square on a chart is even lazier.