Introduction to Routing with Bluewater Racing
I first want to introduce some terms used in these articles, and define them.
A MARK is a waypoint specified by the course.
I will use the term MARK to disambiguate from a waypoint as generated by BWR in optimising a route. For that I *will* use the term WAYPOINT.
A LEG is a section of the race course, defined by 2 consecutive MARKS. Possibly the MARKS may not be consecutive, skipping over one, if neccessary (see below).
My usage of the terms MARK and WAYPOINT also nicely corresponds:
- To reality, what we call them IRL
- To objects created within BWR.
You can create marks, which just like on the race course, are static points used to define routes. Now, a route does not always refer to an optimised route – when it does I will specifically say ‘optimised route’, as a ROUTE in BWR is just any path defined by marks or waypoints. Think of it like this: An optimised ROUTE has a start and end mark, and contains multiple segments defined by waypoints. Don’t worry this will all become clear when you start to actually use the program – which, by the way this is intende to be a somewhat interactive series (of tutorials?), in that there will be accompanying work to do within BWR to illustrate things.
While multiple legs can be routed with BWR, if the leg is more than 12 hours long, and the next mark is relevant to the final route (ie a mark to be rounded with a significant course change), it makes no sense to route beyond the next mark. Sometimes in SOL, a mark will actually be irrelevant to the course, for example it may also lie on the rhumbline to the next mark, and so it should be ignored for the purposes of routing (either using a router or SOTP). As routers are most valuable for the longer ‘ocean’ races, you will most often then, be only optimising a single leg within a race.
At this stage, we won’t get into actually creating marks and routes to be optimised within BWR, but rather I will provide an example file for you to experiment with – and you DO need to play around a little to become familiar with not only the software, but how it performs on your personal machine (optimisation is a very complex process, so higher powered machines are better here) – its ‘limits’ if you will.
First off, download and install BWR. I suggest you download the full (largest) distribution, the only difference between that and the ‘lite’ version is the level of map detail, and while it is possible to download the high detail maps later on – it is just easier to do it right from the start. If you have a slow connection or for whatever reason don’t want to download the high detail map version, the lite version if completely fine – and it will make almost no difference to your routing.
I am going to make an organisational recommendation here, but you don’t have to follow it, it’s just easier for you (especially in the long run) if you do. Install BWR to ‘C:\SOL\Bluewater’. Now within this SOL folder, create another sub-folder called ‘Races2011’, and make a new subfolder here for each race you use BWR on from now on. In it you should save a copy of the polar, all the grib files you download, and the startup file for Brainaid’s NMEA Proxy if you decide to use it (this will be introduced later in the series).
You should even make a new text file for keeping any quick notes you may want to make during races. Just call it race.txt or something – well that’s what I call mine anyway. This is quite useful to keep many bits and pieces – reminders, things you want to take a closer look at – tricky decisions and some info that will help you to judge later if you got it right (for example, you may note the relative location of the closest boat and compare later).
Doing this, you will also build up a nice little archive of all your SOL races over time 😉
Also record your result in the race.txt file. Get into the habit of making notes each race, and a) more ideas for things to note will come to you the more you do it b) you will get better results on SOL – because you will be thinking more and later looking back to analyse certain situations…
During the installation, be sure to click ‘Create Desktop Icon’.
Regardless of whether you follow my advice on creating this SOL folder, it is important to know exactly where you have installed BWR to, and to make that an easily accessible folder, as you need to place the polar file in a sub-folder where you installed it to. It is not a usual recommendation, but wait until you have completed this first introduction before reading the manual, as it deals with ALL the concepts in BWR and I will deal with only a small subset here – sometimes not explaining what certain things I mean, mean (yet).
Once installed, you will notice there is a sub-folder called ‘polars’ – and this is where you MUST place a copy of any polar you wish to use with the program. Just quickly – for each route in BWR you specify a polar to use – for example if file called boat.pol, then you just tell it ‘boat’ for the polar – ie, you don’t specify the ‘.pol’
There are also ‘grib’ and ‘races’ subfolders, but you won’t always use these, especially the grib folder (infact when using for a SOL race, you should NEVER use the grib folder). These folders are defult folders where BWR will open up whener you are browsing for a file of that type – ie when browsing for a grib file, it will start you in the ‘grib’ folder. I say you shouldn’t use that particular folder when using BWR for SOL races, because with up to 4 new grib files per day, it will get full pretty quick – and also the names of grib files is quite cryptic, so I recommend you make a new folder somewhere for each race.
For this introduction, we will work with a simple 400 nm downwind leg, of the coast of New Zealand
SO, here is a zip file containing a gpx ‘race’ file, a polar file and a grib file for the weather – and a pdf version of this article. These 3 things are always necessary when routing – and there are multiple sources of the last 2, and you will be creating your own race files not far into this series. Unzip the file, right into the folder you installed BWR to, all the necessary files will go to their right locations… Otherwise, open the zip file, and manually move each file into its respective subfolder of the BWR installation (.pol into ‘polars’, .grb into ‘grib’ and .gpx into ‘races’). Now fire up BWR, and open the file Introduction.gpx from the races folder (as i said it will take you straight there when loading a race). You should see a small orange line down on the map near NZ. Next, hit ‘Ctrl-G’ and open the file ‘Introduction.grb’ – and you will see some wind barbs drawn around the area to. Look on the toolbar, there is a group of buttons that control zoom – the one to the right of the ‘-‘ – if you hover the mouse you should see the tooltip ‘Zoom to active routes’ – click that one, and you should see something very like this screenshot:
(NOTE: an update to BWR version 1.52 has been released since I started this, and opening a race file automatically performs a ‘zoom to active routes’)
The first thing to get familiar with is the map controls.
On the toolbar, there are 5 zoom controls: ‘+’ ‘-‘ route grib map – in that order, also there are 4 buttons on the very left: pan zoom dist edit. These change the ‘mode’ of BWR – as you can see it starts up in ‘pan mode’, where you can use the mouse to drag the map around – go ahead, give it a go!
Next is ‘zoom’, this allows you to drag out a rectangle and have BWR zoom to that rectangle – again, play around and get used to it.
The next is ‘dist’, which is like a basic version of the Ruler tool in the SOL client. – it only allows you to draw a single line, and only shows the distance info when you stop dragging the mouse (but you can keep the button down and move it again), but it allows you to determine distance and brearing from 1 point to another on the map.
This is a good time to point something out. You see it displays not only the distance, but also the bearing in 2 different ‘ways’ – Rhumbline Course, and Great Circle (GC) course – and it defaults to displaying the GC course using magnetic bearings. If you don’t know what this means, you don’t need to, but you don’t want it to display this but rather ‘true’ bearings, and for this you need to go to the preferences (Tools->Preferences) and change it on the first tab. WHile your there you may also want to change the ‘Route point diameter’ to something smaller than 5 – I personally use 3, but 4 is good to – when doing detailed routing, or using the GPS feature, the route ‘lines’ just look far too thick when this is set to the default 5.
Ok, so now you have hopefully played around a little with the basic controls and become familiar with them – they are pretty simple and intuitive really, so let’s get to some routing stuff!
The main windows used when routing are the ‘Route Manager’ (obviously) and also the ‘Grib Manager’, but we wont be getting into using the grib manager just yet. So go ahead and open up the Route Manager. The 3 toolbar buttons with ‘stars’ on them are the Route, Grib and Polar managers respectively – the polar manager really isn’t a manager as such, but just lets you view a polar plot of the points in your .pol file and the curves they define (but my Polar Explorer is better 😉 )
So open up the Route Manager and you will see a route named ‘Course’ – when you first create routes they just defulat to a name like ‘r13’ or the like, but you can rename them anything, and this will be covered in a later article. You can see in the Route Manager, along with the route name, the name of the polar to be used for the route, the total rumbline distance of the route, ETA (Estimate Time of Arrival) and ‘Corr ETE’ which is just the number of hours it will take to sail ‘Estimated Time Enroute’. You can resize the Route Manager, and resize the colums by dragging between them, which you will often do as you can see some information is not fully displayed.
Already in this race I have specified the Polar to be used, in this case the Super Maxi polar, so now I would like you to enter a start time for the route. You do this, but clicking the route to highlight it and then click the ‘Options’ button (or right-click the route and hit ‘Options’ – which you sometimes must do as BWR has an odd bug that says ‘Please select a Route’ when you click the options button – kind of happens randomly but not often – if it does this is how you work around it). When you do that you will see a Window like the following:
In the start time field, enter: 2011-04-24 00:00 UTC – this is the date and time format expected by BWR, if you forget it you can just look in the top right corner of the main application window to see an example containing the current time. You can also use a ‘Z’ instead of UTC, and case does not matter. Looking at the Options WIndow you will se a number of routing options, which we will get into later, and also that you can change the colour of the route. SO once you have entered the time (just cut & paste from here if you like) hit Done. Apply just saves any modifications you have made without closing the Window.
Just a note on one of the options ‘Nondestructive’ – what this means, and why it should always be checked and is by default’ is when you optimise the route, it creates a copy and optimizes that, without this set the original route would be overwritten.
Clicking ‘Done’ takes you back to the main window – and look – there is already values for ETA and ETE !! ??
So how can it tell us this without doing an optimisation? Well that is one of the very nice features of BWR – and one very useful for learning and for SOTP routing, it will automatically compute the time to sail any route, under the constraints of the current polar, grib and start time. SO what this is now showing you, is the time it would take if you just sailed straight down the rhumbline.
Now, just to get a feel for how some of the routing options effect the calculation of this time, click Options once more to bring them up, and if necessary, move it so that you can see both the Options and Route Manager windows.
First, change the value for ‘Time Resolution’, which should be showing 2.0. What this value controls, is how often BWR recomputes the wind – so for the period of this value (2 hours by default) BWR assumes constant wind conditions. Change it to 0.5, click ‘Apply’ and you should see the route now takes longer, as reflected by a larger ETE in the Route Manager. So from this alone you can tell that the wind is decreasing, or changing direction or both – but our boat speed is decreasing as we sail toward the mark, reflecting in the ETE because BWR is now computing the time with more information.
Now change the Grid Grid Size value, which defaults to 60 nm (1 degree of longitude at the equator), to 10. Again, after you click ‘Apply’ the route’s ETE is increased. This is similar to the Time Resolution control, but for distance (yes there is a distance resolution, but it’s not the same and will be explained later – and in the manual).
Play around with the Time Resolution and Grid size values to get a feel for how they reflect on the route time. When computing the ETE for a manually input route (like you are now) you will want these values small for most accuracy, but when performing an optimisation you cannot use extremely small values, as this impacts the amount of time taken to compute the optimised route, but later I will discuss this in more detail.
There are helpful tooltips available by hovering the mouse over each input field. Handicap formula means ‘What do we want to minimise when optimising a route’.
So, now to do a route optimisation. Set the Time Resolution to 1, Grid Size to 20.0nm and Max Range to 100.0nm, leave the Distance Resolution at 60.0 and click ‘Done’. This is a rather ‘coarse’ optimisation setting, but will compute quickly and is only illustrative. Now with the Course route selected/highlighted click ‘Optimize’ – you will see an ‘Optimizing…’ window appear with a progress bar. This progress bar rarely reaches the fill width before optimisation is complete, and optimising with the above settings takes about 30 seconds on my machine. Once this is finished you can see the optimised route on the map, also in orange, and a new route in the Route Manager called ‘Course_O’. This new route is what is generated from having the ‘Nondestructive’ checked in the route options for Course. BWR just appends ‘_O’ to any optimised version of a route. What you should see is this:
You may notice the ‘Always on top’ option I have checked in the Route Manager – this just prevents the window from disappearing when you do something on the map etc, and is usually useful, although I should point out it will also stay on top of ANY window you bring up, such as a browser. You can see from the new route, that is it suggesting we basically sail the downwind VMG angles, with a small gybe in there along the way – and this is where the program is also educational – try to work out WHY it recommends that small gybe back toward the rhumbline. Understanding why also helps you determine if you should gybe back or not when actually sailing the route in SOL, as in SOL there will be a performance penalty for the 2 extra gybes, which BWR does not take into account – it assumes 0 penalty for any tack or gybe.
You can quickly see in the Route Manager that while the optimised route is just about 88 nm longer than the rhumbline, but shaves almost 3 hours of just sailing straight for the finish – which is what we would expect sailing downwind VMG angles….
Finally in this Introduction, I will get you to compute a more optimal route, by adjusting some parameters. So, open the Options window for ‘Course’ and enter: Time Resolution=0.5, Gris Size=5.0 and Max Range=25.0, click done and then with the Course route selected click Optimize. This optimization will take longer to compute, but is more accurate than the first – which is one of the balancing acts you must perform when deciding exact parameters to use, but time and experience will help you here, as no hard and fast values can be set as i mentioned faster computers will optimize faster, so be able to use smaller values for more detailed and accurate routes.
Anyway, you should see this, (I redefinied the colours for each route to make them more distinguishable):
You can see, it has produced an even longer route, but one that is about 7 minutes faster.
This concludes the Introduction of this series, play around with some of the values we changed here when optimising the route a 2nd time, to get a feel for how well your particular machine can do the computations. As a guideline, routing for a race usually takes me 7-10 minutes given the length and parameters I choose.
Also – READ THE MANUAL! And feel free to try out creating marks and courses of your own before the next tutorial comes out.
You can also use the BWR race files I put on the Race GPX files, under the ‘bwr’ link for each race – these are already setup with some initial reasonable routing parameters set (and any marks slightly offset if they happen to be on land, which we well also talk about later)
Bye for now!