oTidalRoute

[Rasbats]

I have been experimenting with a tidal routing plugin, using tidal current gribs.

Tested using Grib1 and Grib2 files from "bsh.de".

With Grib1, sending a json message provides the tidal current speed/direction data needed (See the screenshot). With Grib2 the json message does not seem to produce a result.

Should json messages to grib_pi (Grib 4.1) work with Grib2 files?

Mike

[Gilletarom]

hello Mike,

Originally Posted by Rasbats

I have been experimenting with a tidal routing plugin, using tidal current gribs.

Tested using Grib1 and Grib2 files from "bsh.de".

With Grib1, sending a json message provides the tidal current speed/direction data needed (See the screenshot). With Grib2 the json message does not seem to produce a result.

Should json messages to grib_pi (Grib 4.1) work with Grib2 files?

Mike

It's interesting. What do we need :
- From the starting point,
- From the point of arrival,
- Information wind
- From the current information,
- A feature of the boat (polar)
- Avoidance of land that could be on the path ....

And hop ...

Gilletarom

[Rasbats]

Notice that the gribs that do not work with the plugin do not display a Weather Table in grib_pi (Example for the English Channel/North Sea from "bsh.de" is attached). Somehow the recordset that the weather table is using (and the json message is working with???) do not have the tidal data.

As an aside I found the Weather Table (right-click menu option) has the current direction 180 degrees in error. Cursor data is correct. Flyspray item added for this:

FS#2172 - Weather Table for tidal current shows direction 180 degree in error

Mike

[seandepagnier]

why not make the tidal current data available to the weather routing plugin?

[rgleason]

Sean, I like that idea.
Also for weather_routing_pi how about a "Report" that would should the
wind direction & magitude (vector) and current (vector) at each point along the calculated route?

[Rasbats]

Sean,

Tidal current gribs from Index of /MyOcean and ftp://ftp.bsh.de/Stroemungsvorhersagen/grib1/hires_exp/ can be opened at the same time as other gribs for wind, pressure etc. Could these be incorporated in Weather Routing?

With oTidalRoute I am looking at a very basic electronic reincarnation of paper chartwork ... course to steer to allow for tide; calculated hourly (maintain rhumb line) or allowing for all the tidal current predicted for the passage with just one course (accept drift to port/stbd but regain final desination). At the moment I am only looking at straight lines from A to B, with an option to change the departure time to make best use of tide. Would a json message from any of these calculations be useful?

Mike

[seandepagnier]

The wr plugin can just use the tidal current data then if it is in grib format once it's loaded by the grib plugin

[rgleason]

Mike can you summarize. Status of your plugin and advise if WR will run and respond to those tide gribs?
I like this because tide is almost as big a factor as wind. Unfortunately or part of the world does not have these grobs.

[Rasbats]

After a mistake in estimating tidal currents last Summer, on a passage from Rosslare, Ireland to Pembrokeshire (St Brides Bay), I decided to put some more work into this plugin.

Tidal gribs are used. These are available from:
Sailing Weather Online
sftp.marine.ie/

This thread describes how to get the Irish gribs.
https://www.cruisersforum.com/forums...bs-200341.html

I have not tried using these gribs with the weather_routeing plugin.

Alpha tarballs available here:

https://cloudsmith.io/~mike-rossiter...lpha/packages/

• The plugin is intended for OpenCPN 5.8.4
• No need to make a .gpx file at the start. The route is read directly from those available in the OpenCPN route manager.
• The logic has been changed. If the route has different speeds for a particular leg this cannot be used. The overall planned speed is used.
• For ETA the tidal current at each EP and waypoint can be shown.
• The EP is calculated using the tidal set and rate at the point of departure on each part of the route, the EP or the waypoint.
• Manual is not yet updated. The old manual is here:https://opencpn-manuals.github.io/ma...ute/index.html

Comments and bug reports are welcome. Bug reports (Issues) are best reported using github. The repo is here:
https://github.com/Rasbats/otidalroute_pi

Mike

[AedanC]

Mike,

Why don’t you just use the tidal gribs from marine.ie together with weather gribs of your choice with the normal weather routing plugin? I’ve done this and it appears to work. Just set both gribs as inputs.

Cheers,

Aedan

[Rasbats]

Originally Posted by AedanC

Mike,

Why don’t you just use the tidal gribs from marine.ie together with weather gribs of your choice with the normal weather routing plugin? I’ve done this and it appears to work. Just set both gribs as inputs.

Cheers,

Aedan

Yes, this does work but ...

• Needed to easily compare the effect of tide with up to 6 different ETD
• WR_pi does not allow the import of a route that has already been planned.
• Estimates of CTS along the route was needed. Ability to make the next waypoint without tacking was assumed.

Generally I will have tried to reach a departure point which allows a passage without a beat to windward. This was the reason that I ended up at Rosslare.

Mike

[AedanC]

Originally Posted by Rasbats

Generally I will have tried to reach a departure point which allows a passage without a beat to windward. This was the reason that I ended up at Rosslare.

Any plugin with that aim is good in my book. I look forward to giving it a try.