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Polar diagrams in MaxSea TZ

Following the post called “Boat characteristics and learning to wally!” I had a number of mails about polar diagrams see also the comments to that post from Peter Gustafsson.

Polar1I can confirm that MaxSea TZ does have a comprehensive polar diagram creation option. It does not assume that the port and starboard speeds are symetrical (like some software). And you can create the diagram automatically

Polar2You can then edit the results to take into account special considerations on the day that you made your recording – such as sea state.

You can also store diagrams according to differing sail sets that you are likely to use.



Routing 7 of 7 : - Conclusion & Oscar Ceremony :-)

Oscars1 I do hope that you have found this series of articles delving into optimal routing software interesting. My personal objective was to learn a lot about routing – and I certainly think I did that. I also thought I would find what was the “best” system on the market – no chance – I am afraid life is not that simple!.

One thing I have found is a new and deep respect for the software developers behind these system – as well as their obvious skill and passion for sailing. While I realise that there may well be teams of developers at some of these suppliers – their is always the original author – so all credit to Nick White (Expedition); Dave Brayshaw (Advantage); Peter Schofield (Seatrack); Brice Pryszo (MaxSea); Brad Christian (Coastal Explorer); Graeme Winn (Deckman).

One of the criteria I set for myself was that I wanted to find the system that I, as an amateur and “average” sailor would find was “easy to use”. Perhaps that would be the clue to finding the best. BUT even here I found that all the TableA and TableB products, although they have different user interfaces, are all understandable – once you put some effort into understanding the inputs and outputs. So the “easy to use” test almost doesn’t apply since you need your brain switched on anyway to understand the objectives and the dynamics of what is going on with optimal routing in the first place.

In terms of the routing algorithm, there is a key difference between all the systems and Advantage by Dave Brayshaw – as you can see from his article on routing algorithms in Seahorse . Even though Dave’s argument is appealing, there certainly are a lot of expert sailors using the alternative isochron based methodologies.

Routing 7 of 7 : – Conclusion & Oscar Ceremony 🙂 → Click here to continue reading →


Routing 6 of 7 : A Chart by any other name...

Most sailors are well aware of the difference between Raster and Vector charts. I have access to both on board plus of course real paper – albeit gradually getting out of date 🙁 I think we are all past having long debates about which format is better. You will probably have huge amounts of storage on your laptop or various USB drives – so long as you archive and backup all those terribly interesting digital photos and videos!.

If you are like me you will just download and store all the charts that you can get your hands on for the waters that you sail. If you are in N American waters then the process is easy. At the very least you can just download the free (vector)  NOAA ENCs charts – latest edition notices for paper charts are here

NOAA Raster Navigational Charts® (NOAA RNCs) are full-color digital images of NOAA’s entire suite of paper charts. NOAA provides weekly updates to the RNCs, which are available for free. NOAA RNCs are official data that can be used in many types of electronic charting systems, including Raster Chart Display Systems (RCDS) and Electronic Chart Display and Information Systems (ECDIS)

Vector charts are more suitable for manipulation by software programs attempting to calculate optimal routing – especially if it comes to manipulating stored data about obstacles; charted dangers or merging charted data with data that you yourself may have stored using the PBG type functionality.

Routing 6 of 7 : A Chart by any other name… → Click here to continue reading →


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 !

Routing 5 of 7 : Algorithms → Click here to continue reading →


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

Routing 4 of 7 : Boat characteristics & learning to Wally! → Click here to continue reading →