Route Planning with GRIB - Work in Progress

[PjotrC]

Tore...

Correct, Route Properties lists wind speed in Beaufort scale.

When comparing Grib Display Control values with Route Properties table please make sure that you are looking at the same GRIB record - the one corresponding to the ETA you are interested in. SW4 is expected on your route since 28th September, around noon. It is not very clear from the screenshot, but it seems it shows the GRIB for 27th September, midnight. This might explain the difference.

No other plugin will work with 2.5.926... only grib_pi and dashboard_pi, which are built with the special interface and included in the test kit.

Thanks again for trying.

Piotr

[siff]

Originally Posted by PjotrC

I have added a Wind Column to the Route Properties Dialog. Given some starting time, this lists forecast wind direction and speed for all waypoints against the GRIB displayed on screen.

For the moment I use only a single, manually selected GribRecordSet, and I do not set next leg speed from the forecast/polar diagram yet. This should not be too difficult, but first I would like to settle the Plugin interface, which seems the hardest part.

I took an earlier Forums - Post 639485">-IRJDSUNE9932123321222xxeww-advice, and extended the set of optional plugin methods to pass a "double" value together with a well-known-identifier. It may go to all plugins, and an answer is expected from some plugin (first answer offered is accepted and sufficient). I imagine that in the future there might also be a method to gather responses from all participating plugins, but I have no need for this now.

I attach the (surprisingly small) working patch based on 2.5.0. I'd appreciate very much any comments and further advice (or maybe the definitive source for the interface to exchange data with plugins...). This is a trial, working version, so I do not split this now into Plugin Protocol Patch and GRIB Route Planning Patch - it is clear what file does what, I think. I have tentatively given some numbering to API versions etc. just to keep the visible difference from base release.

Many thanks in advance for hints.

Piotr

well it is interesting to know the wind you will encounter on your trip. but optimal routing starts on a different basis. You must first have the polar performance of your boat. then you take the wind from the start pointg and look for the different points you can reach in different directions for maybe 4 hours. And from each of these points you start again and so on until you reach your destination. The best route beeing the first one which goes on your endpoint.(see attachement)

You can afterwards add rules to avoid regions of strong winds and so on .. I am afraid, this is not so easy as one could imagine at first.

I would be happy to participate, but i am not very good at coding. Anyways coding it just the last part of the trip ...

[sinbad7]

Piotr..

Yes of course,must be getting tired,taking a break now,
Looking forward to future enhancements.

I hope this feature will in the future also be compatible with other plugins.
I am not so technically oriented but I understood that we ARE presently using the new upgraded plugin engine? Would not be convenient to have parallell OCPN systems installed depending upon which plugin you are using.

Thank for a great new feature,I shall be playing with it to get familiarized.

Tore

[PjotrC]

Originally Posted by sinbad7

Would not be convenient to have parallell OCPN systems installed depending upon which plugin you are using.

Sure, I only posted the trial 926 kit to preview new functionality and gather some feedback. Although it is possible now to generate all current plugins to work in this way together, it is not the right thing to do. The right thing to do is to properly extend the interface to accomodate data sharing needs between plugins and main program structures. It will happen sooner or later, because it is necessary for plugins to do any work with waypoints/routes etc. However, I am not really in position to define this, as there are many issues involved. On the other hand, I do need this functionality underway, so here is just a trial/demonstrator...

Many people will be disappointed, seeing that there is no decision tree pruning, no optimizing function, but once out of Internet access and out of supply of fresh GRIBS, usually the excitement quickly fades away... It is not so difficult to make as one might think at first, but the OCPN effort is better spent elsewhere, since people are doing great work on weather tools already. In practice an optimizing weather router is a shore-based tool, and there is no real need to integrate it closely with OCPN. It is sufficient just to exchange some waypoints and routes with a planning tool, what GPX does well.

[sinbad7]

Piotr..

Thanks for the extensive explanation and for introducing this interesting pre-planning feature. There is of course no problem running a parallell OCPN for this purpose.
I understand the provision of a suitable standard plugin interface is problematic at the moment but I am sure our specialists will find a way in time.

At the moment I am using the 'Additional information' feature of OCPN to collect GRIB data from zyGrib or Ugrib without having to leave my OCPN chart.

Thanks again for your ideas and efforts.

Tore

[sinbad7]

Piotr..

Can you tell me how you calculate the grib forecasts in the Route Manager?

For example my present Grib display control has collected GRIB data from the 27 Sep to 2 Oct every 3 hours. If I set the departure data/time in my route example as 28 Sep 09:00,will your forecast for the entire route (at least to 2 Oct) read and evaluate ALL the GRIB data listed in the Grib display control,i.e. from 28 Sep to 2 Oct,or just the data corresponding to the departure date,making it neccessary to refresh the grib data for each leg of the route. If so,could this not be automated?

Tore

[PjotrC]

Tore,

For displaying forecasts and calculating waypoint ETAs in Route Properties I use all the GRIB records available in the single file selected by user.

It means that no matter, which GRIB record is currently displayed, the Properties will look at all available data _within this file_. If you are displaying a record belonging to a file which is not the newest in current directory, OCPN will not look at the other files.

I just posted (opencpn_2.5.928_setup.exe - 4shared.com - online file sharing and storage - download)) version 2.5.928 with a very useful feature added:

If Departure Time is set, the GRIB display can be synchronized with Route Properties Dialog.
By selecting a row (Waypoint with ETA) in the Route Properties the GRIB displayed on the screen automatically corresponds (best fit) to the selected ETA.

Parallel install and backup essential... it is just a trial...

Enjoy,

P.

[PjotrC]

Just two screenshots from testing...

I compare the ETAs computed with the same GRIB, same route, and same polar curve set by OpenCPN and Bluewater Racing tool ( Bluewater Racing ).

In both a rather simple and a quite complex scenario the difference is 2-3 hrs on a ca. 100 hrs run. For OCPN I need to add more waypoints to the route, as Bluewater recomputes the speed at given time intervals, while OCPN - at waypoints only. The tests show that in practice this should work sufficiently well.

[PjotrC]

So, finally a good winter-time application for OCPN....

I added a helping tool for the Append Waypoint to Route context.

If there is a Route Properties Dialog shown, with a Departure Time entered...

and

If there is a GRIB Dialog shown, with appropriate corresponding GRIB selected...

then

OCPN at each added waypoint will synchronize the GRIB display to reflect the current weather situation,
and will display the polar diagram, showing where the boat can go from last route waypoint during the same period of time.

Additionally, the rubber-band-new-route-segment-info will include the time-to-go and GRIB-or-plan-expected-speed.

Of course, all this can be switched off by selecting no polar curves.

Enjoy,

Piotr

PS. In the examples attached I used the Bluewater Racing polars for a Farr52. The "red" route is constructed by hand, the "green" route is automatically generated from Bluewater Racing for the same GRIB, polar and initial route, Canaries to Gibraltar (always an interesting one).

PPS. Test set 2.5.1006 download from javascriptpenNewWindow('http://www.4shared.com/file/HRKhpiT3/opencpn_251006_setup.html').
Parallel installation and backup essential, as usual.

[PjotrC]

For some reason the attachements to the previous post are missing. They are here:

[sinbad7]

Piotr..

Downloaded your latest version,made a route and downloded the latest grib for the area. The grib has 7 time periods. I tried selecting the first line showing the header but did not work. Selecting any one of the 7 time periods will only give a valid forecast for that time surely? How can clicking each waypoint then give a correct forecast?

Regds
Tore

[PjotrC]

Tore...

Selecting _any_ of the 7 periods will select the whole set in this file for the planning purpose.

In your screenshot I see that indeed you are trying to go against W-WNW wind ...

Cheers, and thanks for trying,

Piotr

[sinbad7]

In your screenshot I see that indeed you are trying to go against W-WNW wind ...

Cheers, and thanks for trying,

Piotr

Not quite,although the route is partially obscured,you will see the previous waypoint has a higher latitude,ergo,I'm going in a SE direction,WITH the wind.

Have not as yet grasped the complexity of the scenario illustrated with the green and red route lines but I will perservere with further study and experiments.

Congratulations with a capturing winter passtime...

Tore

[PjotrC]

Originally Posted by sinbad7

Not quite,although the route is partially obscured,you will see the previous waypoint has a higher latitude,ergo,I'm going in a SE direction,WITH the wind.

Right, I see now... I was mistaken by the 1.0 knot leg speed, consistent from the start of the route. Why that? It must have originated from your polar curve, but I would expect a higher speed going downwind 4-5 and 7B? This is why the simulation stops only at the 6th waypoint - your GRIB set is valid only for 5 days, so no forecast after 10/11 and the speed reverts to the plan speed of 6 kts. Please check the polars, you will find information in the log file.

Thanks again,

Piotr

[sinbad7]

Piotr..

My example was just a crude sample and did not contain sensible data.
I am still trying to digest the finer details of the system,a great mystery for us mere mortals,give me time.

Thanks and regards
Tore