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Routing 5 of 7 : Algorithms

At last we come to the heart of the issue at hand, the optimal routing algorithm.

This is where the software must now manipulate:

  • The planning criteria such as waypoints, arrival time, departure times and so on
  • Real time instrument data, and any fine tuning parameters stored by the user eg. True wind adjustments
  • Boat characteristics and polars either general or specific to the boat
  • Tidal stream data both general from charts and specific based on local knowledge or higher quality data from the supplier
  • Weather data both actual and forecast
  • Collision avoidance such as AIS, MARPA, charted obstacles, user defined areas.

Not to mention the job of outputing data to instruments and to the user via a suitable user interface that makes understanding as well as user response easy and relevant.

Quite a feat of programming !


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Routing 4 of 7 : Boat characteristics & learning to Wally!

This is part 4 of the quest for the best optimal routing calculations within ECS/ECDIS systems today. In this posting I wanted to consider the use of polar diagrams and data that represents the performance of the boat in a variety of wind conditions.

Catalina30-Polar Of course wind cannot be taken in isolation when comparing your actual boat performance against any given polar diagram. The manufacturers polar diagram will tend to be an idealised version of what your boat will do at its design weight and under good sea conditions. The most likely source of polar table information is a velocity prediction program, or VPP: a computer program that uses information about the boat’s design—the hull lines, rig plan and so forth—to predict the yacht’s performance.

The image to the left for example, shows a pretty good polar diagram supplied for a Catalina 30 – and here you can see it notes that this was with a 150% genoa and the boat had a folding propeller.

Software designers sometimes incorporate other factors at this stage that will either automatically or manually take into account wave height, and other boat performance characteristics such as surfing down large waves for example. For a glimpse of the maths involved in calculating polar diagrams have a glance at this presentation from Pau Herrero, Luc Jaulin, Josep Vehi, & Miguel A. Sainz


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Routing 3 of 7: Data Inputs (wind, pressure, tide, streams, wave heights etc..)

There is a famous saying with computer software GIGO – garbage in garbage out.

So this review of software based routing calculations starts with the data that is being input.

There are 5 main sources of “data”:

  1. The expert assessments and factors stored in the software by the authors, and their expert consultants such as Michel Desjoyeaux
  2. The instruments on the boat itself feeding data in real – time
  3. The behaviour of the boat – its specific sailing characteristics – especially as represented by a polar diagram(s)
  4. The adjustments made by the skipper/navigator based on experience, or experiment.
  5. Data from external sources especially GRIB data.

It is this GRIB data that I will look at first.


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Routing 2b of 7 : Routing planning and optimisation an extra brain as well as a pair of hands...

In my previous posting I listed those systems which were clearly aimed at the racing sailor. This is not meant to be a drawback – it depends what your objectives are as a sailor as well as your capability and skill level. They very accomplished pieces of software and provide at the very least a source of information to the cruising sailor about the higher art of race tactics, tuning and performance.

The next group are NOT inferior to the the first (TableA) in any way –  but I feel that they are less likely to be underutilised by the normal cruising sailor than the ones in the racing stable above. I feel that they may be operated in more of an amateur manner with less fine tuning than the top racing packages. This is a backhanded complmemnt to SeaPro and MaxSea – systems which are very well accomplished on the racing circuit !

It may seem strange to put MaxSea in this table since there are dozens of race wins attributed to it… but it is included as testament to the ease of use of its interface that I believe makes it more intuitive than the race packages above. It is truly a race class piece of software but it can easily be used by a cruising sailor with its elegant “TimeZero” interface.


Routing 2b of 7 : Routing planning and optimisation an extra brain as well as a pair of hands… → Click here to continue reading →

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Routing 2a of 7 : Routing planning and optimisation an extra brain as well as a pair of hands...

For the experienced sailor – and the world’s best sailors and navigators all use sophisticated routing and route planning software – this software is a critical source of information , while for the less experienced (like me) it is an education as well.

In the course of this research I have corresponded and talked with a number of the developers of this type of software, and I have been impressed not only by their sailing credentials, and their skill at software development, but also at the care with which they have struggled to meet the challenge of creating viable and trustworthy systems that can add value to the cruising and the racing sailor – without taking away any of the responsibility of a skipper.

It is a very exciting area of sophistication for systems aimed at the leisure sailor and is bordering on the class of systems that are truly ECS/ECDIS systems for commercial vessels – and I certainly feel that using this type of software – and putting effort into understanding it – will make me a better sailor – I will never be a  Michel Desjoyeaux – but I may benefit from his and other expert’s experience because it is sailors like these that are being consulted in the design and logic of the routing software. I will use the phrase ECS/ECDIS in  this series of articles to keep in mind that the systems being looked at are a class above the normal chartplotting systems availble to leisure sailors, and are in fact already sold to the commercial market or are capable of being sold in that market.

I will be posting my findings in a variety of sections relating to:

Routing 2a of 7 : Routing planning and optimisation an extra brain as well as a pair of hands… → Click here to continue reading →

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