Weather Routing

[Gilletarom]

Originally Posted by Thonglor

Hello Gilletarom,

I've been playing around with this plugin in recent days. ..........

No offense intended, just trying to understand your intentions and the realisation in OpenCPN & WR!
For a free tool I think it's already fantastic what has been implemented!

BR Tibor

What are my intentions by "criticizing" this or that defect of OpenCPN .... or of these plugins?

On the one hand, I've been using OpenCPN for 13 years, and that shows how much I care about this software. On the other hand, it's true, it's already good as it is....

But, whether we like it or not, the competition is severe with other software. And if we want OpenCPN to remain a software appreciated by many sailors, the faults it may have must be corrected.

Gilletarom.

[rgleason]

Originally Posted by Gilletarom

What are my intentions by "criticizing" this or that defect of OpenCPN .... or of these plugins?

On the one hand, I've been using OpenCPN for 13 years, and that shows how much I care about this software. On the other hand, it's true, it's already good as it is....

But, whether we like it or not, the competition is severe with other software. And if we want OpenCPN to remain a software appreciated by many sailors, the faults it may have must be corrected.

Gilletarom.

Gilletaron I totally agree with you.

[bdbcat]

Gilletarom...
I have looked into the first point you have raised, relative to your particular work-flow.


1. When converting from Track to Route, the boat speed values at intermediate points are simply ignored and lost. I would consider this a bug, of a sort. That is, for your use-case, you want the resulting Route to contain estimated speeds between the successive points, as predicted by WeatherRouting plugin.

On the other hand, this is probably not what is wanted for the general case of converting a Track to a Route. Consider the general case, where some recorded or shared Track is converted to a new Route. When the new Route is actually used, the speed values recorded at each point are of no relevance, since the Route sailing conditions will certainly not match the conditions present when the Track was recorded (last year? another boat?).


So it seems that what is really wanted is to adapt WeatherRouting plugin, adding a feature so that one can "Export" a completely defined "Planned Route", with "planned speeds" included for each leg, as predicted by the plugin. In fact, it may be sensible to remove the option of Exporting a Track, since in OCPN we usually think of a Track as a "recording of some previously sailed adventure".
In either case, this will require a new Version of OCPN to implement. It cannot be accomplished solely from the plugin.
To be sure, I think this is a worthwhile upgrade, and will add it
Your further comments are appreciated..
Thanks
Dave

[Gilletarom]

Originally Posted by Thonglor

Hello Gilletarom,

I've been playing around with this plugin in recent days. .......
But honestly I don't understand the concept of laying a weather routing "layer" over a pre-defined route. The only benefit of doing that (which I'm able to see) is to get a meteogram of the route, i.e. the program calculating what kind of weather you'll get at a certain point in time along your route...........

For a free tool I think it's already fantastic what has been implemented!
BR Tibor

Hello Thonglor, or Tibor,

I come back to you on the usefulness of having a manually constructed route analysed. You only see one.

I see at least two for me who owns a sailboat.
- Know the duration of the course of the route, globally and segment by segment..
- Check, for my sailboat, that it can always have a usable wind to move forward.

Gilletarom.

[Gilletarom]

Originally Posted by bdbcat

Gilletarom...
I have looked into the first point you have raised, relative to your particular work-flow.

1. When converting from Track to Route, the boat speed values at intermediate points are simply ignored and lost. I would consider this a bug, of a sort. That is, for your use-case, you want the resulting Route to contain estimated speeds between the successive points, as predicted by WeatherRouting plugin.

On the other hand, this is probably not what is wanted for the general case of converting a Track to a Route. Consider the general case, where some recorded or shared Track is converted to a new Route. When the new Route is actually used, the speed values recorded at each point are of no relevance, since the Route sailing conditions will certainly not match the conditions present when the Track was recorded (last year? another boat?).

So it seems that what is really wanted is to adapt WeatherRouting plugin, adding a feature so that one can "Export" a completely defined "Planned Route", with "planned speeds" included for each leg, as predicted by the plugin. In fact, it may be sensible to remove the option of Exporting a Track, since in OCPN we usually think of a Track as a "recording of some previously sailed adventure".
In either case, this will require a new Version of OCPN to implement. It cannot be accomplished solely from the plugin.
To be sure, I think this is a worthwhile upgrade, and will add it
Your further comments are appreciated..
Thanks
Dave

Hello Dave, I very much appreciate that you have considered my long post of 07/28/2023 regarding the analysis of a route by WR.

I understood that two requests coexist concerning the use of the analysis of a route with WeatherRouting.

- Those who take an old route to analyze it according to a new, more recent grib. In this case, the old speed data is no longer current.
- Those who create a new route manually and who will use WR to obtain the expected speeds on each segment and the times of passage on each waypoint.

It will also be necessary for the transfer of a route to a peer to leave the speed data and passing times intact.

I also hear the point of view of some users who do not understand why to do this and who consider that WR should only be used to find the fastest route automatically. BUT, I have observed that some users, who are familiar with WR or other weather-routing software, say they prefer to plot their route manually anyway.

I had understood that it was necessary to make modifications in WR and also in OpenCPN so that things go well. I have two other ideas to suggest:

1°) When I draw a route manually, which will be used for my daily navigation, I always make it start from a port and I always make it arrive in a port or at an anchorage. WeatherRouting is usually not able to find a solution. Always create starting positions and arriving out of ports in WR. Would it be possible to show the weather-routing positions of WR on the screen permanently or with the possibility of displaying and hiding them as one can do with WPs in the routes, tracks, and waypoint manager? 'OpenCPN, (or as Jongough allows to show or hide the points of the objects that the Draw plugin manipulates.)


2°) In the case of the analysis of a pre-existing route by WR, would it be possible to designate a waypoint of the route as the starting point of the analysis and another WP as the end point of the analysis.


Dave, it seems that Sean de Pagnier will not be available to participate in modifications and that you will have to make modifications yourself in WR and in OpenCPN. So thank you in advance for the work you will do.

[Franziska]

Hi guys, just a, perhaps stupid or crazy off the shelf thought.

As some folks seem to want to share tracks and have perhaps the option follow a proven track(sometimes that is safer than following a sketchy chart), I think it might be a good idea to include some info on the vessel who created the track.
Like beam and maximum draft and date & time (important in tidal waters).

That way we could perhaps even have some sort of repository of used tracks?

Maybe it's a bit to specialized and might be better suited for another plugin?
As said, it's just a thought...

Sent from my MHA-L29 using Cruisers Sailing Forum mobile app

[Thonglor]

Hello Gilletarom,

your explanation helped me to understand your intentions, thanks! And fair enough - I just hadn't thought of it this way before. For me WR was a method to find out the best route between two points in a given weather. But surely the idea of weather analysis along a route is also a good idea and a good usage.

To be a little hair-splitty: to be more precise in wording I think one could diifferentiate between the OpenCPN functionality called "weather routing" and the purposes that can be achieved with this functionality. I can now see two main purposes:

1) to calculate a route using weather as input (in the form of grib files) => input weather, start point and target point, output route; this is how I would interpret the term "weather routing" itself;

2) analyse weather along a given route => input route and weather, output weather along route (over time). In my point of view this encompasses both purposes "Know the duration of the course of the route, globally and segment by segment.." and "Check, for my sailboat, that it can always have a usable wind to move forward." I would call this a "Route Meteogram" or "Weather Route Analysis" (exactly like the item introduced in the contextual menu by WR).

And with regards to the bug that the calculated speed is not exported to a route created from the "weather route track" I tend to agree with bdbcat on the purposes of tracks and routes. What is wanted is a new functionality "Planned Route", with "planned speeds" included for each leg, as predicted by the plugin, or a real "Weather Route Analysis" report. I attach an example of the earlier referenced LuckGrib - that's what I would call a "Weather Route Analysis".

[rgleason]

The RFE (Request for Enhancement) related to these requests is turning out to be a real whopper. Would someone please start to summarize these and post them in the weather_routing Issues so they can each be discussed further?

Also please keep in mind that WR utilizes a number of other plugins, including

• Grib (weather data)
• Climatology (long term weather data)
• Ocpn_Draw for Boundaries to avoid or stay within.

The functionality of these plugins are important as are the limitations.


Meteo Data screen is essentially derived from Grib.

[crayiii]

Is there a way to view/print a table based on the weather route that shows the hour, position, wind data, sea state, polar used, cog, SOG, etc?

[rgleason]

Originally Posted by crayiii

Is there a way to view/print a table based on the weather route that shows the hour, position, wind data, sea state, polar used, cog, SOG, etc?

Short answer is no, but that is a nice RFE. Please add it to Issues or Tracker.

[yugo_76]

I am having a bit of trouble in WR. It seems that it is suggesting to go totally upwind. How to edit the settings or configure it to avoid such thing? What are the causes of this issue?

[SoggyPaws]

Originally Posted by yugo_76

I am having a bit of trouble in WR. It seems that it is suggesting to go totally upwind. How to edit the settings or configure it to avoid such thing? What are the causes of this issue?

Check your polar file pretty carefully. If your polar says your boat goes faster to windward, that's the way it will route you. We started with a similar boat's (manufacturer's) polar file and thought the speeds were ridiculous for our boat and our style of cruising. So we dialed back the speeds to more closely reflect our boat and our style of cruising (reef early, and avoid nasty weather).

Also, unless you limit how high the wind you want to sail in, it will route you into the highest wind, because (in theory) that's faster.

Would be useful if you posted a screen shot of your polar file and the route that WR came up with. And version of OpenCPN and WR (if not most current).

Sherry

[yugo_76]

I made a route using the Volvo 60 polar file that came with it. Now I've discovered the Polar plug in to create your own. But I'll post it both soon. I think that to avoid sailing computations with almost to the limit in beating the wind, I must not record the polar file in such situation. Hopefully WR will avoid those angles.

[rgleason]

Yugo,
The weather_routing manual has important caveats about polar files and how exactly to make a good polar for your boat. The polar files in the library are collected from everywhere and have had the format made consistent, for use, but have not be verified. If you wish to suggest a better, more realistic polar for the Volvo 60 please attach a file with the extension polar60.txt.pdf for example in a format that is consistent with our other polars, and I will make sure to include it. Thanks. (PS I always thought that polar was fast!!)

https://opencpn.org/wiki/dokuwiki/do...n:manual_basic


https://opencpn.org/wiki/dokuwiki/do...manual_plugins


https://opencpn-manuals.github.io/ma...ing/index.html

Originally Posted by yugo_76

I made a route using the Volvo 60 polar file that came with it. Now I've discovered the Polar plug in to create your own. But I'll post it both soon. I think that to avoid sailing computations with almost to the limit in beating the wind, I must not record the polar file in such situation. Hopefully WR will avoid those angles.

[wholybee]

Originally Posted by yugo_76

I made a route using the Volvo 60 polar file that came with it. Now I've discovered the Polar plug in to create your own. But I'll post it both soon. I think that to avoid sailing computations with almost to the limit in beating the wind, I must not record the polar file in such situation. Hopefully WR will avoid those angles.

After 30,000 miles, I learned not to worry too much about how accurate the polar is. A polar from a similar boat with similar LWL is always good enough. And going through extensive effort to make a perfect polar does not make the results of the weather route any better.

The grib file will not be 100% accurate. If the wind angle is 3-5 degrees off, that is enough for the weather route to predict you on the incorrect tack and put you many miles away from where you should be. The plugin does not use wave gribs or wave polars, and wave height and period have a dramatic effect on sailing speed, pointing ability, etc. Again, putting you on the wrong tack, and many miles off course.

Lastly, the difference between the perfect ideal route and just sailing a rhumb line course is usually very small. In the models I have run and routes I have sailed, I estimate you will gain 45 minutes over 2 weeks, typically. That matters only if you are racing, and the best race teams pay an experienced navigator to find the best route instead of following the predicted route, because the predicted route is never the best route-even with much better software the OCPN and much better polars than you will create.

The weather routing plugin is a great planning tool. It will help you to know what conditions to expect in a few days or a week, and where you generally might be. But unless you are trying to avoid a cyclone or some other major event, the best course is always to sail your boat to the conditions you are in, and not follow the weather route.

Regarding making your own polars. You will want to make recordings and polars for all angles of sailing, at all wind speeds, and different wave heights. So, on a day that it is blowing 15 knots, go out sailing, sail for a while at every heading, and note the wave height. At some point you will have many recordings of wind speeds from 5 kts to 30 kts. Each recording having every sailing angle, and at specific wave height.

Next, gather all the files for little to no waves. Use those to make a polar for calm conditions. Then gather all the files for medium waves and make a polar for moderate waves. And lastly one for larger waves. Then when you run the weather route, select the polar for what sea state you expect.

If you have multiple sail configurations, you will also need to make polars for them, Symmetric Spinnaker, Asym., reefed sails, etc. All of those polar files can go into a single boat configuration and WR will then tell you when to make sail changes.

It is a CRAZY amount of work to get an accurate set of polars. For a boat like a Volvo 60 with a full selection of sails you probably need to make 30 different polar files or more. Hundreds of hours of sailing, and waiting for the right wind speeds it might take you a couple years. But like I said, you are not going to get better results than just using what is close and already there for you.

The pro teams use more sophisticated pro routing software, and the big sail lofts will generate polars for the sails they sail that are mathematically generated. AFAIK that is the only reasonable way to get a complete set of what you want.

All that to save 45 minutes on a 2 week-long crossing.