Navigating the High Seas: Decent, Great, or Terrible?

Does anyone know how crews for shipping vessels navigate the high seas, i.e. Asia-to-US routes?

Is there one software tool that crews lean heavily on (aggregating NOAA+OSCAR data) or internal tools per shipping company?

And for real-time navigation, is it the crew or captain making judgement calls based on experience for fine-tuning?




@Kennebec_Captain Ah, thanks.

I was reading and noticed that wave height is a major factor in performance, per 3704. Environmental Factors. Are crews able to measure wave height today, or do they do so visually from a distance?


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OK, looks like they can measure it indirectly from wind + assumptions or visually.

@Kennebec_Captain, from your experience as a Captain of the high seas, are there situations where you’ve changed the short-term course from a recommended navigation plan based on something you saw that digital data from NOAA or OSCAR didn’t tell you? And if so, why did you change course? Safety, fuel efficiency, reduced hull damage?

Most often we adjust the plan because of changes in the forecast. Shorter duration forecast are more accurate.

I’m on RO/RO our main concern is ship motion. So while the are several factors to consider in routing sea/swell height and direction is usually the most critical followed by wind speed/direction.

If the route takes the ship into unfavorable conditions then we monitor ships motions and weather conditions and adjust our course and speed as required to minimize the risks associated with vessel motion.

There are times when it is not possible to avoid weather in which case we might adjust the course for a better ride, maneuver the ship in a compromise between sailing towards the destination and vessel motion or simply find a course to maintain control and minimize ship motion till the weather improves.

This is from Bowditch ch 37:

This is the system I use under military charter, what the article doesn’t say is the master can email or call the ship router ashore to question/discuss.

There are two general types of routing services available. The first uses techniques similar to the Navy’s OTSR system to forecast conditions and compute routing recommendations, which are then broadcast to the vessel.

Below is what I use under commercial charter.

The second assembles and processes weather and sea condition data and transmits this to ships at sea for on-board processing and generation of route recommendations. The former system allows for greater computer power to be applied to the routing task because powerful computers are available ashore. The latter system allows greater flexibility to the ship’s master in changing parameters, evaluating various scenarios, selecting routes, and displaying data.

The description above in my case is not completely accurate. Updates are emailed to the ship. In cases where the all the routing is done aboard he software aboard ship can be used to find the optimum route as described.

When the ship is receiving routing advice from ashore I can still use the software to evaluate routes but in addition I receive routing recommendations from ashore both by text / graphics and with a route which loads into my and the bridge desktop computer.

@Kennebec_Captain I see. So you are getting information from a centralized source (let’s say NOAA, OSCAR, plus other sources), and then using something on-board (where you may provide inputs specific to your vessel, risk tolerance, and situation, or perhaps things you are noticing that the centralized system cannot see or know) to optimize your route?

What is the onboard system you use under your commercial charter? And do you feel that the combination of centralized data plus what you are inputting truly gives you the most optimized route, or do you wish there is some other data you’d like that just doesn’t exist today or is difficult to get? For example, do you wish that buoy data was available in a much denser form, or do you wish you could see what other vessels nearby are currently doing or conditions others went through in the past day?

At sea, world-wide, the ship gets weather info, warnings etc via GMDSS from SafetyNet and Navtex. That information can also be gotten through the Internet. The ship also can receive weather fax.

This information is all derived by information collected by government weather agencies.

In addition I have available a commercial product WNI WeatherNews Heres a screen shot -

On my desktop computer I can enter my GM, draft, speed and max sea height limit / wind speed limits and the program will calculate the optimum route. I can then modify it and observe the total transit time, ETA etc.

The crew also makes and records systematic weather observations. These are separate and are logged but not entered into the computer. Observations every six hours are sent to the NWS using VOS.

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For long transits, for example Asia to U.S. routes, the limiting factor is uncertainty in the forecasts, not lack of usable data.

And optimized is a term of art, the optimum route is the result of whatever algorithm is used based on available data and given the parameters used. Change any of those and “optimum” route will be different.

EDIT: One important point, in my case anyway the so-called optimum route as created on the ship does not take into account errors or the amount of uncertainty in the forecast. That’s a shortcoming of the software and is a trap for the unaware or unwary.


Some of the ships i’ve sailed got into port just by accident. I can judge the height of a wave pretty good but I don’t know how i got that way.

Thanks for giving me a look into how you route through the open seas – this was super helpful. I’m sure something like VOS helps tremendously and am glad crews do it.

VOS is indeed very helpful to the meteorologists who compute the models with the data. It is particularly useful for determining frontal boundaries and surface pressure gradients. The forecasters accuracy is dependent on real time observations and feedback and I am more than willing to contribute my part for the safety of my crew and vessel.