Weather Routing

[hasse_A]

Originally Posted by rgleason

Hans, I am curious what prof routing software, and what is the data source?

Sorry Rick, we have been on passage the last 8 days from Brazil to French Guyana with no internet so could not reply.

We use SOR. It is actually a software for the shipping industry.
It seem to give good current forecasts. At least for the last passage we made.
I do not know what the source is but maybe I can find out.

See plot.

/Hans

[rgleason]

Thank you hasse_A I am familiar with Sor.

[rgleason]

Sean, See this post re Rtofs coastal tidal currents please.
http://www.cruisersforum.com/forums/....php?p=2425727. They don't include models of these currents yet, however tidal currents is in the mission statement. It appears to be a goal at this point.

[arianna]

I installed the new Open CPN 4.6.1, but the plugins dosnt show. I tried to re install it without luck. Any clew?

[.Paul.]

Originally Posted by arianna

I installed the new Open CPN 4.6.1, but the plugins dosnt show. I tried to re install it without luck. Any clew?

Welcome to OpenCPN and CruisersForum.

The User's Manual for OpenCPN has many clews. The manual is installed on your computer when you install the OpenCPN program. You can access this embedded manual with the "?" toolbar button in OpenCPN. Then select "Help" from the menu.

You can also access the online manual at the OpenCPN.org website:

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

One other clew--since you posted in the "Weather Routing" thread, I think you might be looking for the Weather Routing plugin. The Weather Routing plugin may be downloaded from the OpenCPN.org site:

https://opencpn.org/OpenCPN/info/downloadplugins.html

Edit: If you installed a plugin, but cannot see it on the toolbar, it might be disabled. Select the "Options" tool (wrench icon) and "Plugins" from the Options menu. Then, scroll down through the list of installed plugins and "Enable" the plugin(s) that are missing from the toolbar.

Paul

[rgleason]

Arianna, If you instaled a new version of opencpn, it is undoubtably a parallel install which only has the original 4 plugins. You will have to install your other pi.

[rgleason]

I've been with Sean and he's shown me some things about weather_routing.
My understanding of polars was expanded. My statement here:
http://www.cruisersforum.com/forums/...ml#post2413461

Is incorrect!

Most often when a failure is "Polar Failed" it is due to the polar file not having data that is needed for the winds that are available.

A "Polar fail" can occur anywhere on the chart at any Time, due to a plethora of factors:
1. Light winds and no polar data for winds that light.
2. Heaviy winds and no polar data for winds that heavy.
3. Running out of time.
4. Cyclones in the area causing excessive winds.
5. Grib file has not wind data. "Grib Polar: Failed"
6. Grib file runs out of data. "Grib Polar: Failed"

If "Polar Fails" there is a good reason for it, and our job is to figure out why. Here are some suggestions to help.
1. Open the View > Cursor Position menu popup so you can see what is happening.
2. Check the wind speeds in the area and time at which it fails by moving your cursor around and viewing wind speeds in Grib_pi. Move the grib_pi time back and forth to understand how the wind speeds are changing. Compare the speeds found to the Polar file!
3. In Try moving the Grib_pi Start Date forward a day or two, provided the grib file has that data, then in Weather_Routing Config pick "Grib Time" The try to Compute a routing.

With Sean's help we got some of the polars that stop before completion of a full 1/2 heart. That look like the right image.
http://www.cruisersforum.com/forums/...1&d=1497447402
working, by adjusting the start so the grib file would have adequate wind, or moving the start waypoint further along the track or adjusting the finish waypoint. By doing this we learn what the restrictions are.

In short, there is nothing wrong with these polars or Weather_routing. They do what they are supposed to do. If there is not polar data from 0 knots of wind to 5 knots of wind, and the grib data has 2 knots in a area and time where the boat must pass, the "Polar: Fail" will occur! - If this happens change things so you understand, change the start or end point, change the date of start. Last resort check the wind available during the routing in the area where the failure is occurring.

Here are two examples.

The first one has "Polar: Fail" and the cursor was put right at the end of the routing that was haulted and is showing 2 knts. Please note the Polar to the right in Square "Speed" View. The Polar does not have any data from 0 knots to 5 knots.

The second one has moved the date of the Grib file up to Aug 23 when there are better winds. And it has completed successfully.

If a "Polar:Fails", it does not mean the polar is improperly formatted, it just means that most often the route cannot be run because the grib data does not fall within the wind ranges of the polar.

The other suggestion Sean has made, is to try to have 2-3 of your boat polar files in the Boat.xml that cover the full gamut of winds. If you motor in winds from 0-5knots put a polar in that shows your motoring speed.
If you sail best with full genoa and main from 5-18knts have a separate polar for that. Then have a couple of heavy weather polar files with different sail sets.

Weather-Routing will use all of these Sail Sets, calculate crossovers and then show the sail changes on the route with a little square. The exact sail changes can be seen with the View > Cursor Location popup menu where the exact polar name being used is shown.

[bcn]

Originally Posted by rgleason

A "Polar fail" can occur anywhere on the chart at any Time, due to a plethora of factors:
1. Light winds and no polar data for winds that light.
2. Heaviy winds and no polar data for winds that heavy.
3. Running out of time.
4. Cyclones in the area causing excessive winds.
5. Grib file has not wind data. "Grib Polar: Failed"
6. Grib file runs out of data. "Grib Polar: Failed"

If "Polar Fails" there is a good reason for it, and our job is to figure out why. .

Rich, Sean - a suggestion.
Make the error message explicit:
not "Grib Polar: failed" - "now guess why"
but "Grib Polar failed: Light winds and no polar data for winds that light"
etc.
The program shall know what is missing or can't be calculated. Why not using this knowledge to inform the user?

Hubert

[seandepagnier]

Originally Posted by bcn

Rich, Sean - a suggestion.
Make the error message explicit:
not "Grib Polar: failed" - "now guess why"
but "Grib Polar failed: Light winds and no polar data for winds that light"
etc.
The program shall know what is missing or can't be calculated. Why not using this knowledge to inform the user?

Hubert

I explained to rick it is not so simple. It can only give the exact reason for each point on the map.

For example, maybe it cannot explore east because the wind is too light and the polar doesn't define boat speeds in such light wind. It cannot explore west because the wind is too strong and the boat doesn't define these speeds.


In this case should the error message say (polar failed: light winds and strong winds) ?? It will probably do this often.

It can stop for a variety of reasons (see constraints) such that changing any one setting out of dozens of settings could allow the route to complete.

[bcn]

Sean....

so perhaps simply publish what your are describing:
when the algorithm has to stop, name the constraints that are failing in this point.
"Routing failed: 1...., 2...."

And obviously when changing some parameter at start or on the track, you will not get with the same set of constraints to a given point (almost impossible to get to the same point with the same heading and time stamp I would suppose).

Naming what have failed will help the user to improve the parameters he can influence. Complete the polars for example.
And of course there are "impossible routings" with no solution.

Hubert

[rgleason]

I started to list the constraints, just following the program menus, and was going to number them, but if the User hits "Reset" the configuration defaults to the simplest most sure way to get results (for the most part). The default settings are all noted below. This covers a large number of variables. The user will have to change some of them in order to get any results.

Note: We are going to have to rewrite the Weather_Routing Manual because it has changed. I'll work on the numbering of constraintsthat should possibly be in the compute failure notice.

Weather_routing is remarkably flexible, with that comes complexity. New users must not dive in changing settings without understanding what they are doing or how it affects "Computation". Generally the "Reset" settings are the most reliable settings available and can be left alone, however there are some settings the user must set manually in order to get any results!
1. Grib_pi - Freshly downloaded wind, current & wave grib larger than the area needed and more days than expected. Set the grib at the start and then move it one or two frame intervals forward, or set the Grib data and time at what you want.
2. Weather_routing_pi - Start Time. From the Configuration menu, hit "Grib Time" to set the start time for the routing. There are other ways to do this, but use this way to start.
3. Next create Start and End waypoints and select them in the configuration menu.
4. Then go through all the Constraints and Options and check them against the defaults listed and read the description, changing the settings as noted. Hopefully this will result in your first "Completed" Weather Routing.

Start & End
Define Start & End Locations in the first menu
Start Grib_pi and/or Climatology_pi
Set Grib_pi to the date and time you want to use.
Then go to the Weather_routing Config menu and pick "Grib Time"
Generally leave Courses (relative to true wind) alone.
From 0 to 180 by 5 degrees is fine.
For Time Step I generally start larger and once things are working
go smaller, The Course distance governs what the Time step is.
Divide the time expected to sail the course into 10 and use that number for the Time Step.
Then adjust as needed.

Constraints (if you are having trouble, set these to the defaults below)
Basic
Max Diverted Course 76 degrees
Max True Wind 100 knots
Max Apparent Wind 100 knots
Max Swell 20 meters

Additional
Max Latitude 90 degrees
Tacking Time 0 (disabled)
Wind vs Current 0 (disabled) Factor for waves and hobby horsing
Max Course Angle 180 degrees
Max Search Angle 120 degrees

Cyclones
Avoid Crossing Cyclone Tracks Unchecked
within X months X days 1 month 0 days

Options
Time step 1 hour 0 min 0 sec

Basic
Detect Land Checked (when first starting, uncheck it)
Detect Boundary Unchecked
Use Currents Unchecked
Wind Strength is 100 percent

Advanced
Inverted Regions Unchecked
Anchoring Unchecked
IntegratorNewton

Boat
Data Source First use a freshly downloaded grib of the entire route area (a little larger than then route), making sure that it is for a big enough time interval. Then set the Grib_pi at least one frame later than the start time.
Grib Unchecked You will need to check this.
Climatology Disabled You can leave this disabled when you are starting. You can run routes using Climatology alone, or you can use the 30 year Noaa data averages to extend calculations for a long trip both at the start and finish. There will be an indicator on the preferred route when the data source changes.
Last Valid if Data Deficient Unchecked If your grib file is not long enough checking this can help.

Boat Files
Path to XML File: Boat.xml (stores which polar files to use)
Polar Files: At least one polar, preferably 3 polars covering all wind ranges 0-40

To Add a polar you must select from the directory or provide a compatible polar for your boat created by a service running a VPP program, by recording actual performance while sailing in non-current areas and times, or by using the useful VPP program built in to weather_routing described elsewhere. The other file operations are Up, Down, Edit, Add, Remove which all operate on Polar Files.

If the polar stops at about 45 and 150 true wind, and does not cover < 6 knots and >8 knots then you will need to create additional polars to define the upper and lower wind ranges or you will not be able to run routings without getting "Polar: Failed" notices. If you use the motor from 0-5 knots you can make a motoring polar quite easily. Also you can create an estimated polar for winds greater than your normal range, assuming a different sail set, such as second reef in main and second reef in jib, or storm jib.

Having polars for "light" "normal" and "heavy" wind will help prevent "Polar:failed" routings when grib are winds too light or too heavy and there is no polar data available.

Keep in mind that to plot the polar you must pick the Plot tab and highlight one of the boat's polar filenames. It is useful to select "polar" or "speed" views of the Polar down at the bottom. Polars are normally shown with True Wind Direction, but there are other selections at the bottom.

Cross Over Chart is not working in windows at the moment, but crossover is calculated when there are at least two polar files for a boat. The graphic will show you what winds and sail set you should be changing to.

Stats Is a useful summary for sailing performance which gives you Polar Targets at a given wind speed.

Once you have your Polar files loaded into the Polar window remember to SAVE BOAT or Save as Boat if you want a new XML file. This saves the [Boat].XML file that stores the set of boat polar file names used for your boat. The other [Boat].XML operations Open Boat, Save Boat and Save as Boat are self explanatory.

Now you are left at the Weather Routing Configuration menu. You've configured that, so hit Close.

Now double check and make sure you have Grib_pi open and using the file you want. Then highlight the Configuration you just set up and hit Compute. Hopefully it will complete. If it does not complete look at the calculations and see where the optimal route stopped.Step the grib file forward to just where the optimal route stopped. Then hover your cursor over that end of the route and determine what the wind are, your polar file may not have an adequate wind range. So you can add a lower or higher wind polar with a different set of sails. Or you can move the grib file forward one or two days in hopes there are better winds. Hit "Grib Time" in the Weather_routing Config menu. Close it and then hit compute again. The route may complete.

Please feel free to add/comment on this beginning.

[rgleason]

While working on WR Manual, I tried defining 3 polars that would cover the full range of wind speeds 0-50 and then decided to try a routing through Irma, just for fun.

[rgleason]

Here is another test using Irma grib files from today, with multiple polar---.pol files and polar-test.xml (boat.xml) with routing from Cuba to Puerto Rico.

I notice that there is a 3 hour interval where the winds will go up to 48 knots which is seen by the WR calculation and indicated as Max Wind Speed= 38 knts, but if you simply click through the 3hour grib intervals you will not see the higher wind speed.

Using Grib_pi interval
Thurs-Sept7-1500 = 11knts
Thurs-Sept7-1800 = 12knots.
grib_pi is not showing the intermediate times and winds.

However weather_routing_pi registers the maximum wind speed as 33 knots because it's Interval was set on 1 hour and weather_routing does interpolation.

If we were to set the interval to 1/2 hour, the max wind speed would probably be higher, perhaps 45 knots.

[rgleason]

Weather_routing_pi uses a [Boat].xml to store multiple [Polar].pol filenames to be used with the Current "Configuration".

Many users have been having trouble "Completing" Weather Routes due to "Polar:Fail" which is often because the one polar they have used does not span the entire wind range of the grib file being used.

Users are encouraged to create a separate "[polar].pol" file for each set of sails used (even for reefing). For Example: (LW-light wind, MD-medium wind, HW-heavy wind), such that the full range of tws is represented, say 0-60knts.

To help users when starting out, I've created a "polar.xml" file that references four or five "polar-xxx-xxx-xx.pol" files that account for various wind ranges, noted in the polar file name.

NOTE: These files can be inspected and edited using a text editior such as Notepad++ You are encouraged to learn how they work (particularly the *.pol files). It will assist you in creating good polars for your boat.

-----
Polars-Pol.zip.doc

Remove "doc" and unzip these files and place them in the directory below.

Stepped Range True Wind Speed Files
Polar-LW-Power-tws-0-6.pol (use power in light winds)
Polar-MW-tws-0-20.pol
Polar-HW-tws-20-60.pol

Single File with Full Range True Wind Speed 0-60 knots
Polar-TEST-tws-0-20+60.pol (simple smaller file)
Polar-TEST-tws-0-60.pol
Polar-TEST-tws-0-60x2.pol (in tws increments of 2 knts)

Polar.pol File Location (windows):
"C:\ProgramData\opencpn\plugins\weather_routing\da ta\polars"
Polar-Test-xml.zip.doc

Remove "doc" and unzip this single file named "Polar-Test.xml" and place it n the directory listed below.
Polar-Test.XML file Location: (Windows)
C:\ProgramData\opencpn\plugins\weather_routing

These Polar.pol and Polar-Test.xml [Boat.xml] file can be used by new users to get started. Proper use will avoid Compute failures of the type "Polar:fail".

[rgleason]

Weather_Routing_pi User Manual has been updated.
https://opencpn.org/wiki/dokuwiki/do...eather_routing