Integration with QtVlm - Data files and Import/Export

[rgleason]

As an example, read from "La Tavern" qtVlm Forum :
VMG, is "simply" the bearing that gives you the fastest approching speed to the goal using the current wind.

VBVMG does the same, but integrates a tack to the goal.
As a consequence, the VBVMG is often closer to the orthodromial route than VMG (which does not mean it's always faster).

So if I select the VBVMG option with a WP of my choice the boat will sail itself there including tacking (for example if I am away for a few days and can't check in) ? [Question is discussing when in Virtual Racing mode on Loop du Mer]

Yes ... that's it -And when your WP is reached your boat will sail VBVMG towards next race WP

New topic available into wiki ...

Also a very good Wiki section on qtVlm Menus

[rgleason]

After using Sailfish Yacht Analyzer (one VPP program available other than the Excel spreadsheet PCSail.xls see Forum thread) to create polars for a Bristol 32 with 140% Jib, I was able to save the file as an xml and then edit it down. (See attachments -I added the doc to upload. The working one strips out xml code.) The values were cut and pasted the values into qtVlm csv format and tested (several times) to get things looking right.

Then I made another polar using Sailfish Analyzer downwind spinnaker values below 120 degrees and less than 14 knots.

The final csv files were copied into C:\Program Files\qtVlm\polar and loaded from inside qtVlm under Boat Settings. See the attached files for the stages of the process. I found it easiest to use Notepad++ for editing and creating all files rather than Excel.

I added 40 knots at the end and copied the 20 knot values for each angle because I thought maitai said we should do that. I think the polar speeds are a little ambitious as the boat goes 7.5 max on a reach down the backside of big waves. Here's the 140% jib version

TWA\TWS;8;10;12;14;16;20;40
0;0.000;0.000;0.000;0.000;0.000;0.000;0.000
40;3.900;4.200;4.800;5.150;5.900;7.100;7.100
45;4.288;4.776;5.225;5.678;6.183;7.863;7.863
60;4.935;5.454;5.948;6.427;6.936;8.466;8.466
70;5.098;5.629;6.132;6.572;7.062;8.335;8.335
80;5.154;5.687;6.145;6.562;7.017;8.007;8.007
90;5.075;5.599;5.994;6.442;6.810;7.577;7.577
110;4.652;5.139;5.584;5.924;6.273;6.953;6.953
120;4.373;4.885;5.305;5.705;6.066;6.717;6.717
135;3.954;4.529;5.028;5.463;5.856;6.566;6.566
150;3.744;4.371;4.890;5.357;5.770;6.519;6.519
165;3.627;4.263;4.807;5.270;5.695;6.434;6.434
172;3.581;4.203;4.746;5.193;5.612;6.360;6.366
180;3.483;4.119;4.657;5.122;5.537;6.262;6.262

Here's the 140% + Spin version

TWA\TWS;8;10;12;14;16;20;40
0;0.000;0.000;0.000;0.000;0.000;0.000;0.000
40;3.900;4.200;4.800;5.150;5.900;7.100;7.100
45;4.288;4.776;5.225;5.678;6.183;7.863;7.863
60;4.935;5.454;5.948;6.427;6.936;8.466;8.466
70;5.098;5.629;6.132;6.572;7.062;8.335;8.335
80;5.154;5.687;6.145;6.562;7.017;8.007;8.007
90;5.075;5.599;5.994;6.442;6.810;7.577;7.577
110;4.652;5.139;5.584;5.924;6.273;6.953;6.953
120;5.101;5.678;6.208;5.705;6.066;6.717;6.717
135;4.754;5.341;5.851;5.463;5.856;6.566;6.566
150;4.295;4.917;5.437;5.357;5.770;6.519;6.519
165;3.892;4.543;5.089;5.270;5.695;6.434;6.434
172;3.581;4.443;4.980;5.193;5.612;6.360;6.366
180;3.483;4.346;4.901;5.122;5.537;6.262;6.262

Maitai, I hope these look in the right format to you.

I then tried it out with qtVlm and a fresh 8 day grib file. Largely on a reach this 32' boat got about 1/2 way to Azores, from Long Island Sound, New England, 1111 orthdromic nm, at average 6.25 knots, in 7d 9h 50m, average TWS 20k (which is a lot for this boat)

I then tried the 140jib+spin polars and it made 10 minutes difference.

Then just for fun I tried the "boat_class40.csv" polars and that boat made made it to the Azores within the grib file period, 1979nm 6d17h55m at 13.74 knots. What a difference 8' makes!

Generally I created a "Routing" first, then in the Edit Routing, General Tab, checked "Convert to route using this prefix" and apply. Then I would go Edit a "Route" select that new route that was created and be able to check "Optimize without simplification" and watch it work. Its kind of cool. Then check "simplify" to reduce the number of points.

This was a pretty good exercise. Next I'm going to import the "route"" into OpenCpn.

-Note I need to find out how to measure Righting Moments RM2, RM20 and RM40 to be able to plug accurate numbers into Sailfish.

[rgleason]

Export an optimzed and simplified Route from QtVlm to Opencpn is very easy.
In QtVlm go into Edit "Route-xxx". One the first tab, pick Copy. This copies the route to the clipboard. Then open Opencpn and right click on the ocean and pick paste.
-Simple.

In OpenCpn you can right click and pick "Track" and a track will be made with which preserves a "timestamp"" if you want a record of where the Grib had planned for your boat to be in its journey. It basically freezes the planning of the route for comparison later.

[rgleason]

Route and Track transfer from QtVlm to OpenCpn

Here are thre images showing results of:
1. QtVlm - Creating a "Routing" in QtVlm then converting it into a "Route", then optimizing the route without simplification, then simplifying the route and reducing the number of marks. Then editing the Route and selecting copy in order to transfer the route or track to Opencpn.
2.OpenCpn - Pasting the Route or Track in the clipboard into Opencpn.







While in QtVlm you can also Route export as gpx file and then use OpenCpn Route Manager to import gpx file.

[maitai]

Great explanation thanks Rick.

Concerning the polar the format is correct. I don't think it's correct to add a last column at 40TWS with the same values as 20TWS. That means the boat sails at the same speed for a given TWA from 20kts to 40kts, which is just unrealistic imo. In this case and especially since you mentionned 20TWS is already a lot for this boat I'd put 0 BS in all the 40TWS fields. That way qtVlm will interpolate and for instance BS at 30TWS will be half of BS at 20TWS, and as a consequence the routing module will understand that 20TWS is better than 30TWS for your boat. It's not compulsory to have a last column at 0 (although it's more realistic imo, who is making ground at 80TWS?). In you example the 40TWS column is just useless, because if qtVlm founds more wind than exist in the polar it just takes the last value available.

I also noted that your best angle downwind at 20TWS is almost full downwind (173 twa), which sounds a lot, but of course you know better.

In qtVlm too you can freeze a route, for instance if you want to compare 2 routes generated with different polars or gribs.

[rgleason]

Maitai, thank your for your assistance and explanation of the 40 knot column.

Are we allowed to put a row in for any angle? IE Sailfish polar angles are not always 15 degrees. - I think just put in rows for known angles with the values and it worked, but I just want to be sure. The reason I ask is Sailfish listed polar information from 60 to 180 and also listed the optimal angle and boatspeed upwind and downwind for each wind speed. I then took the average angle for optimal upwind and used that.

I can sail in 25 knots to 30 knots, but it is with a completely different sail setup (small jib reefed, or storm and double or triple reef on main) In fact, with the 140 jib I start furling at about 15 knots or I take a reef in the main.

Should I have a different polar for each of these sail conditions, or should I try to work the sail changes and corresponding speed into a single polar as I tried to with the Jib140+spin values? I suppose for the purpose of routing longer distances, it would be better to have a single polar that has the sail changes worked into it..... It would be nice to know what the sail plan/changes are along a given route... I suppose that would get complicated.

The "Routing" or "Route" could change line type
dotted running
dot-dash run tacking
dash reaching
solid upwind or change the colors.

A thicker line could represent stronger winds ... just a thought.

These values are derived from Sailfish Yacht Analyzer a VPP program, most of it looks about right, but the next step is to start recording a nmea data stream and get some actual values (hopefully next summer). I hadn't thought about the best point downwind at 173, that the VPP program and how I've set thee boat parameters, but as you noted, my experience tells me it is a little higher than that.

I could also do some tests on the boat to determine righting moment RM2 RM20 RM40, if I knew the procedure, to improve the Sailfish polar values.

[maitai]

Rick,

You can put whatever TWA/TWS in the polar, no problem. No need to be regular either. Only constraint is that all cells must have a value.

It's in the todo-list to manage several sails setup, where qtVlm will choose the best one and tell you what sail configuration you should be using. As it is now as you said you have to switch polar manually and have a "mixed" one to route long distance trips.

I note the idea about the route color and line type. Note that you can already display the route details when changing the grib's date (route->edit->"display data from roadbook at grib date" checkbox).

I must confess I have no idea what RM2/RM20/RM40 are... can you elaborate a bit?

[rgleason]

Awesome about the sails setup and qtVlm choosing and advising, good idea. Then we can keep separate polar files for each sail setup and sea state which is less confusing.

Note that you can already display the route details when changing the grib's date (route->edit->"display data from roadbook at grib date" checkbox).

Do you mean from main menu "Routes" then "Edit Route", <select> then second tab "Route Details"? There are good color coded details and graphic wind icons (maybe where I got my colored route idea).


OR are you suggesting I can get to that Tab through the actual route's date indicator at the beginning of the route...by right click on the date, then I should pick "Set the grib date" This puts the boat location back to the beginning at the start time for the route and the date and time show up in the upper right corner. When I select the arrow button to move the boat and grib for 3hr, 6hr, 12hr as set, the boat is show on


Now I am trying to figure out

..."display data from roadbook at grib date" checkbox)

Ah, I see. Opening "Routes" / "Edit Route" <select route> at the First Tab down under Options section.
"Freeze Route" Checkbox which you mentioned. That stops any changes and locks the time, grib and route, I assume.
"Display data from roadbook at grib data" Checkbox - Check it, hit apply


and "Data at Interpolation Point for Route" Window appears with Wind/Current Data -TWD,TWS,TWA,AWS,AWA,Tack Port or Starboard graphic,CD CS and Boat & WP Data -HDG,BS,COG,SOG,CNM,DNM - All good information!

This changes dynamically as I click on the blue grib arrows that change the Grib Data and the planned boat location. Very nice Maitai.

[rgleason]

...do tests on the boat to determine righting moment RM2 RM20 RM40, if I knew the procedure, to improve the Sailfish polar values.

RM stands for righting moment at 2 degrees, 20 degrees and 40 degrees. I suppose you put an empty barrel on the end of the boom a measured distance out and start filling with water at 8.13 lb/gal or whatever and measure the heel at 2 deg, 20 and 40 deg. Then calculate the lever arm and weight to get the moment, probably in ft-lbs for this program. http://www.techsail.com/ (Use IE, Firefox does not work as well)

I am just guessing here... I also put in numbers from what I thought was a similar boat and then played with them to get appropriate heeling angles for my boat.

Sailfish executes VPP formulas from a book mentioned on the website. I guess I have to get that book.

[rgleason]

Maitai, in "Routes" / "Edit Route" / <select> When you check "Display data from road at grib date" The Data window pops up for the current grib at the appropriate route location for the boat (as planned at that time). I started to really look at the data and now have a question about what CD and CS mean. Also CNM and DNM?

Also for some reason CD stays at 180 degrees and CS stays 0. Is this related to currents and because this grib has no currents in it, the values are 180 and 0?

Thank you

[rgleason]

Loaded question: Does this "Display data from road..." window have a similar window for actual readings from Nmea? It seems like the programming is similar, with the exception of the live link and filtering.

[rgleason]

Freezing a Route: To freeze a route you must have defined the route with two marks or poi, not with the boat at the start! It appears that the "Display Data" window is no longer responding to the grib in this situation (I do not know if that is correct action) but the Route Detail Tab is all there.

Incidentally you can unfreeze the route by unchecking.

[maitai]

Rick,

CD stands for Current Direction
CS stands for Current Speed
CNM stands for Course to Next Mark (i.e. orthodromic heading to next POI)
DNM stands for Distance to Next Mark (i.e. orthodromic distance to next POI)

If no currents-grib is loaded CD and CS should say N/A, which is the case in the roadbook from route->edit. I'll fix that in the next one.

If you freeze a route the only relevant information is ETA at each POI. The rest is lost/irrelevant because it depends on the grib and polar the route was generated with.

There is no similar "book" for NMEA data, although you can display the raw NMEA data (for debugging purposes mainly).

[rgleason]

Let's see this is a little confusing to me at first.
Below, under Boat and Waypoint Data below we have COG and SOG..

CD -the word "Current" applies to tide & current, obviously, not COG.
CS - the word "Current" applies to tide & current , NOT meaning "present speed" , not SOG.

I am wondering how this is calculated. Ah, now I realize it is predicted current from the Grib file. Is that correct?

[maitai]

Your heading (HDG) and your Course Over Ground (COG, which is HDG compensated somehow by CS and CD) is not always equal to CNM, because for instance you don't want to and you cannot sail full up-wind.

In short HDG is your instant Heading, while CNM is the heading to the next mark. If wind direction allows it they are equal, otherwise not.

It's confusing...

EDIT: And yes "Current" means tides & currents, not "at the moment". If you know a less confusing word for current I'll take it immediately (and not currently lol)