The Law of Tonnage

[Refueler]

You‘ve basically got it: calcs aren’t relative to the bridge, the ship’s speed through water doesn’t relate to the same reference frame as the yacht’s AIS (GPS), and there is always an error term. To avoid any possibility of calibration risk, many of the large shipping co.s - I am told - set a minimum open water safe clearance of at least 0.5m.

????

Wrong - sorry. Calcs are relative to the position of the radar scanner. Which is usually on the mast above the accommodation / Wheelhouse.

I am trying to understand what you mean by "the ship’s speed through water doesn’t relate to the same reference frame as the yacht’s AIS (GPS), and there is always an error term" ?????

Shipping Co's regard miles not parts of miles .... if I was OOw and I passed 1 mile off another vessel in open waters - the Master would ask me if I was looking to have dinner on the other vessel ...

Old sayings that carry good sense :

A collision is two idiots trying to occupy same space at same time.

Why pass 1 mile from each other when you have the whole ocean to play with ?

Why wait and make large alteration when early and less solves the day ?

And one that may make you smile ....

If you look at radar screen and looks like someone threw a bowl of rice on it .... what do you do ? Swap down range to lose most of them ... (its actually what you do and then take each target as it comes instead of trying to sort many at once !! Typical new operators mistake).

 

[Refueler]

As a vulnerable and venerable yottie, I'd be thinking 'It's his responsibility to do something to avoid a very real Risk of Collision. If he hasn't done something evident by - say - just under 2 miles ( in accord with Rule 16 ), it becomes MY responsibility ( Rule 17 ). What are my options.....?'

My 'series of bearings' will have established a Line of Constant Bearing exists, which is 'a Risk of Collision exists'.. How can I change that...?

I could ease sheets to change speed to change the LCB. Might that be enough to resolve the situation under Rule 17?
I could stop where I am. Might that be enough to resolve the situation under Rule 17?
Could I change course? Might that be enough to resolve the situation under Rule 17?
What combination of the above might resolve the situation AS I SEE IT while retaining my capacity to manouevre should my initial 'change' prove insufficient?
What might he do to screw up all those judgements? Do I have a Plan B for Rule 17?

I would ensure my own engine was available for immediate manoeuvre.

I had a situation in Baltic returning from Sweden .... a small container ship gave me cause for concern ... not easy on a yacht to keep taking bearings to ascertain Risk of Collision ... but it was obvious this was going to be VERY VERY close and I could see his bow wave !!

What did I do even though technically I was Stand On vessel ? (I was heading East ... he was heading South on my port bow) .....

I immediately took a round 360 turn to stbd to be CLEAR that I was getting away from him .... he carried on not making any change ... the mess I had in cabin was unbelievable from his wash ...

Once we settled clear and I had his name ... (UK flag as well !!) - I called him on VHF and asked him if he had even seen me ... he replied that he had plotted me for some distance and CPA was about 1 cable ... and asked what was MY problem ....

I asked him if he was aware that 1 cable cannot be determined on a yacht pitching and rolling about and is FAR TOO CLOSE anyway ... that his bow wash was to me a BIG wave ...

He dismissed it all with silly remark - to which I basically replied that in all the years I had stood on the bridge I had never done what he just did ...

 

[Refueler]

When entering the details of one’s AIS class B transponder you have to give the details of the coordinates of where the positioning GPS antenna is. (metres from centre line and from bow IIRC) I assume this is used by the software to help in calculating CPA’s. I assume you have to do something similar with Class A setup procedures.

Its only an indicator on AIS and not to taken as absolute. It's based on GPS vs GPS positioning and you should know that that jumps about ...

The real CPA and info used by OOW is based on Eyeball and Radar ..... the radar plot is then based on the location of the scanner on the vessel - usually aft on the main mast unless a Passenger vessel etc.

 

[Refueler]

I really don't know.

My standing night orders when surveying were to call me with CPA under 0.2 nm on survey ops, often against the traffic flow in separation zones a lot depended on my confidence on my Mate .

I'm still here and the boat is still working - I wish I was still aboard .

W

WOW !!!! 0.2nm !! THAT close ???

 

[Refueler]

Yes, , because I expected my Mate to make a prudent descison Below that I wanted to be called , especially if things weren't changing I wanted to be called to th bridge .

I trusted most of my mates 110% - a few less so .

Towing sonar and other equipment meant little options other than to ask other ships to respect our work, almost all were acceping and were happy to help.

W.

I worked for CGG and then later for Western Geophysical on Seismic work towing 3 mile cables .... 0.2nm ????? Blimey if a boat got that close - I'd have expended all Very Pistol warning flares ... have already called the Techs to deepen the cable depth ...... an AB with bino's to keep eye on tail buoy .... and trying to decide what I would write in the report to Company !!

 

[john_morris_uk]

Its only an indicator on AIS and not to taken as absolute. It's based on GPS vs GPS positioning and you should know that that jumps about ...

The real CPA and info used by OOW is based on Eyeball and Radar ..... the radar plot is then based on the location of the scanner on the vessel - usually aft on the main mast unless a Passenger vessel etc.

Agree 100%. If you were comparing bearings with one end of the ship with the other somethings wrong! Radar usually gives pretty accurate CPA info and it’s the go to source for most watch keepers. .

 

[dom]

????

Wrong - sorry. Calcs are relative to the position of the radar scanner. Which is usually on the mast above the accommodation / Wheelhouse.

I am trying to understand what you mean by "the ship’s speed through water doesn’t relate to the same reference frame as the yacht’s AIS (GPS), and there is always an error term" ?????

Shipping Co's regard miles not parts of miles .... if I was OOw and I passed 1 mile off another vessel in open waters - the Master would ask me if I was looking to have dinner on the other vessel ...

...If you look at radar screen and looks like someone threw a bowl of rice on it .... what do you do ? Swap down range to lose most of them ... (its actually what you do and then take each target as it comes instead of trying to sort many at once !! Typical new operators mistake).

Lots wrong here I'm afraid.

First, with respect to different references, this should be clear enough. For example, a ship may measure its speed through the water, which will differ to GPS/AIS reference frames owing to tide, etc. Nothing wrong with multiple data sources, crews just have to be aware of them and training explicitly reflects this.

Second error terms, these are a central concept to modern ship navigation equipment, including the gear I saw an the bridge of a large container ship in Hamburg 3 weeks ago. No measurement is perfect, no vessel can hold a perfect speed, heading, etc. It is imperative to be aware of this, as emphasised time and again by said company. The vessel's maneuvering prediction software resolves this into an area of potential collision at some future point in time. The ships will wish to avoid this entirely. And of course the entire ship's dimensions are considered, not just whether the radar antenna will make it.

Third, as to shipping co's regarding miles, not part of miles: this is not so 0.5nm, or 0.75nm separations are often specified in confined waters, separation schemes, etc.

Fourth, SOLAS currently makes no specific provision for AIS. In any event, to minimise the risks from faulty data and other references, radar remains the primary collision avoidance mechanism. For only this can provide a reliably accurate measurement of the chosen target’s relative course and speed. These are in turn the most important factors in deciding upon a suitable collision avoidance strategy.

To bring this back to something useful for a yottie:

1. Fit an AIS transceiver. They are not expensive.​

​

2. Fit a decent radar reflector, or better still a Radar Transponder.​

​

3. Of course every yacht should stand ready to execute a Rule 17(a)(ii), or 17(b) emergency maneuver but the vast majority of ships and almost all of the large ships will scrupulously apply the IRPCS. Be aware that the ship may have altered course before a non-AIS equipped yacht can discern such action. Basically, think once, think twice, before assuming that the ship is a lout!​

​

4. In the open sea, hold a steady course and try to avoid tacks, etc. when within 3/4 miles of a ship that may have already initiated a preemptive avoidance maneuver.​

​

Finally, on say a X-Channel trip, if anyone has ever wondered why so few avoiding maneuvers are required and why an unlikely number of ships sweetly pass a mile or so ahead or behind, it's because many have already altered course 3/4 miles out.

 

[Achosenman]

Agreed. IRPCS is the preferred way to know what the other vessels master/watch officer is doing. If the expected action does not occur, or occur in a time frame you are happy with, IRPCS helps yet again.

Crossing the channel and negotiating traffic entering or exiting VTS is an excellent demonstration of the rules smoothing the way.

The fly in the ointment would be fishing vessels...I must have made at least six course changes during one encounter starting at 2 miles, they still managed to contrive a conflict...

 

[zoidberg]

The fly in the ointment would be fishing vessels...I must have made at least six course changes during one encounter starting at 2 miles, they still managed to contrive a conflict...

Ah! That'll have been a certain notorious beam trawler out of Looe, I reckon. Father and son, outdoing each other in 'hooligan'....

 

[Achosenman]

You had the pleasure too I see...

 

[john_morris_uk]

I think a few of us might have had the misfortune of appearing to act as homing beacons for fishing vessels at some stage in our seagoing careers.

 

[PilotWolf]

I worked for CGG and then later for Western Geophysical on Seismic work towing 3 mile cables .... 0.2nm ????? Blimey if a boat got that close - I'd have expended all Very Pistol warning flares ... have already called the Techs to deepen the cable depth ...... an AB with bino's to keep eye on tail buoy .... and trying to decide what I would write in the report to Company !!

We never towed anything that long. That was almost 99l% lateral/ parallel clearance, much more than that we wouldn't have been able to work as much of the work was in the Dover Straights TSS . CNIS used to put us in their nav warnings, the biggest issue was having the space to turn at each end of the grid without getting in anyone's way or pi$$ing off ships enroute.

W.

 

[Uricanejack]

Lots wrong here I'm afraid.

First, with respect to different references, this should be clear enough. For example, a ship may measure its speed through the water, which will differ to GPS/AIS reference frames owing to tide, etc. Nothing wrong with multiple data sources, crews just have to be aware of them and training explicitly reflects this.

Second error terms, these are a central concept to modern ship navigation equipment, including the gear I saw an the bridge of a large container ship in Hamburg 3 weeks ago. No measurement is perfect, no vessel can hold a perfect speed, heading, etc. It is imperative to be aware of this, as emphasised time and again by said company. The vessel's maneuvering prediction software resolves this into an area of potential collision at some future point in time. The ships will wish to avoid this entirely. And of course the entire ship's dimensions are considered, not just whether the radar antenna will make it.

Third, as to shipping co's regarding miles, not part of miles: this is not so 0.5nm, or 0.75nm separations are often specified in confined waters, separation schemes, etc.

Fourth, SOLAS currently makes no specific provision for AIS. In any event, to minimise the risks from faulty data and other references, radar remains the primary collision avoidance mechanism. For only this can provide a reliably accurate measurement of the chosen target’s relative course and speed. These are in turn the most important factors in deciding upon a suitable collision avoidance strategy.

To bring this back to something useful for a yottie:

1. Fit an AIS transceiver. They are not expensive.​

​

2. Fit a decent radar reflector, or better still a Radar Transponder.​

​

3. Of course every yacht should stand ready to execute a Rule 17(a)(ii), or 17(b) emergency maneuver but the vast majority of ships and almost all of the large ships will scrupulously apply the IRPCS. Be aware that the ship may have altered course before a non-AIS equipped yacht can discern such action. Basically, think once, think twice, before assuming that the ship is a lout!​

​

4. In the open sea, hold a steady course and try to avoid tacks, etc. when within 3/4 miles of a ship that may have already initiated a preemptive avoidance maneuver.​

​

Finally, on say a X-Channel trip, if anyone has ever wondered why so few avoiding maneuvers are required and why an unlikely number of ships sweetly pass a mile or so ahead or behind, it's because many have already altered course 3/4 miles out.

I suspect, Refueler and I are from an older generation. The considerations, decisions and actions of a young OOW might be different to those I might have made a generation or back.
If they are different, your post suggest they are using improved technology to reduce safety margins rather than making thier actions readily apparent to the other vessel “Visually“.
Possibly due to poorly written Masters Standing Orders or conflicting directives from ashore.
Truthfully I don’t know, I haven’t been to Hamburg for decades. Or transited Le Manch recently.

I can say back in the good old days, using a grease pencil, and an azimuth ring, there was lots of traffic lots of small vessels even some crazy fishermen.
The scale I operated on was considerably greater than most small vessels would imagine. A pair of Binos was my primary aid to navigation and collision avoidance.
Of shore I operated on the 12 and 24 miles range, a transit of the Channel probably 6 and 12, I had usually acted by 6 , on Ocasions I might use 3 and 6 if it was particularly busy or there was a lot of small stuff to pick my way through. Perhalps at
Dover, Gib or Mallaca
Distance for time action, or CPA varies with the vessel, the manouverbilty , location, traffic, traffic density, the type of vessel, crossing, reciprocal,, overtaking , weather, visibility, passing ahead or astern,
Comfort level will vary.

As Refeuler said, passing within a mile in open water, why? It will draw comment.
The OP video clearly shows the Tug and Oil Barge pass a Large container ship at give or take a few meters 1 cable. Confined waters.

Drive with considerations for others, Just like like you should on the road, As we all know from driving not all drivers do.

About 40 years ago, When I was still very young and STCW 78 had not been implemented. A particularly crusty and formidable Old Man. Called me up to the bridge. To him, I was a form of life, who should be seen and not heard.
“Right sonny, what are they and what are they for?” I was utterly confused, I couldn’t figure out what he was pointing at, The only items were the wheel and the telegraph. It must have been something more important, He was getting a bit annoyed.
Eventually I said rather nervously it’s the Telegraph Captain.

After I had explained to his satisfaction what the wheel and telegraph were and how the worked.

”Right Sonney” “The Mates had some long day working cargoes“ “You Have the 8 to 12 tonight”
“You Know what they are and how to use them“

“Use them if you have to, then call me.”

That is all I can remember of the Handover to my first ever watch on my own. A small tanker from Sharjaha to Bahrain lots of traffic.
I used the telegraph later that night and called him. Chief Engineer was quite upset and said some very rude.
They often are when you mess with their engines.

The Old Man came up when called. Was actually surprisingly pleasant, Even called me Jack instead of Sonny.
Asked what was going on, I told him, All he said was very good carry on, Let me know when we are clear.

He spoke to the Chief, After which the Chief was a bit more polite.

I asked about it after.
he told me never to worry about the ,chief he will deal with the chief.
You know what the limitations of the ship and the engine are.
He also told me
No Master worth his salt will ever come up to the bridge and critise you for acting safely to avoid collision. Even if it was not what he might have done.
If you need to use the telegraph to slow down. Slow down.

It is a big deal to go from full sea speed to slow, The engines don’t like it, It will attract everyone’s attention, So will going hard over.

I sailed with other Masters who perhaps “weren’t worth their salt”
There are unfortunately quite a few who will critise you for messing up an ETA, Fuel consumption stats or just not having the same willingness to take a risk as they do.
They're not worth their salt

Ive never critised an OOW for taking early substantial observable action t avoid collision including speed reduction.

I sure as heck will if they don’t.

One of the worst things I’ve ever seen written is call the master if you have to alter course more than or Alter speed.
Case in Point USN Destroyer, The Officer on watch didn’t call the Captain.

Rules like this give someone reasons not to call. Or to limit action.

Even so over the years, I had a few close encounters of the 3rd kind. Which were reported.

 

[requiem]

I agree, but I’d assumed that entering size of vessel and where the antenna was meant that the software took it into account.

Might be a vain hope though and I start to concentrate as soon as the CPA is under a mile or so.

The docs for the software I use state:

• CPA gives distances based on center of Own-Ship and target. This assumes vessels maintain course (COG & SOG), regardless of current ROT.
• BCR gives distances for centers of Own-Ship and target, not their bow or stern. The calculation assumes vessels maintain (COG & SOG), regardless of the current ROT.

I believe for larger ships the magic abbreviation is "CCRP" for "Consistent Common Reference Point" from which all related calculations (target CPA, bearing, etc.) are taken. Thus you can have different sensors in different parts of the ship and their data will be corrected so that they are all relative to the CCRP. (Yes, if you lose the heading sensor this stops working.)

AIS can provide the data to make those fancier calculations, since you could use the ship's size, position, and heading to determine which part of the ship might need some fresh paint. That's a terrible idea, in part because of the items Dom mentioned. (A brief presentation semi-relevant to this may be found here.)

 

[Uricanejack]

Hmmm, I’m no electronics guru. We hire gurus as required, to install and set up gadgets.

The scanner is the point for CPA. If other gadgets give something different, and conflicting info. Installation guru gets a call, come fix PDQ.
The scanner is usual pretty close to where the bridge is, probably slightly aft of conning position,
This May result in a slight error or variation from a visual reference. Which may effect perspectives.

This error in perspective is very small or even negligible on an aft bridge, small on mid ships bridge. Very noticble on a forward bridge.

 

[dom]

“You Know what they are and how to use them“

“Use them if you have to, then call me.”

That is all I can remember of the Handover to my first ever watch on my own. A small tanker from Sharjaha to Bahrain lots of traffic.
I used the telegraph later that night and called him. Chief Engineer was quite upset and said some very rude.
They often are when you mess with their engines.

The Old Man came up when called. Was actually surprisingly pleasant, Even called me Jack instead of Sonny.
Asked what was going on, I told him, All he said was very good carry on, Let me know when we are clear.

He spoke to the Chief, After which the Chief was a bit more polite.

I asked about it after.
he told me never to worry about the ,chief he will deal with the chief.
You know what the limitations of the ship and the engine are.
He also told me
No Master worth his salt will ever come up to the bridge and critise you for acting safely to avoid collision. Even if it was not what he might have done.
If you need to use the telegraph to slow down. Slow down.

It is a big deal to go from full sea speed to slow, The engines don’t like it, It will attract everyone’s attention, So will going hard over.

I sailed with other Masters who perhaps “weren’t worth their salt”
There are unfortunately quite a few who will critise you for messing up an ETA, Fuel consumption stats or just not having the same willingness to take a risk as they do.
They're not worth their salt

Ive never critised an OOW for taking early substantial observable action t avoid collision including speed reduction.

By the sound of it tolerances are indeed tighter and — as with cars — improved technology can certainly bring it’s own set of risks. Foreseeing them isn’t always so easy.

Your wonderful writing style took me straight back to a book I read as a child - Joseph Conrad’s Typhoon. I was half expecting Captain MacWhirr to walk onto the bridge!

I think you should write a book

 

[Refueler]

I took my 2nd mates (first licence) in 1977 ..... and the ColRegs then were in 'flux' as the new ones had come in but old rules were still remembered by examiners and old hands.

"Uricanejack" I think is from similar stock to myself ... and makes a point about later generations maybe using techno and 'cutting it a bit thinner' ...... that was a major point of contention in the 1970's ColRegs .... where Radar was mentioned .... and the expansion of the stand on vessels being able to take action as well.
Those two factors led to huge debates as to how to interpret ....

Such as : A radar equipped vessel may proceed faster in restricted visibility ....... second : a stand on vessel may take action if the action of give way vessel alone may not avoid collision (I do use own words there on purpose to illustrate the problem of interpretation).

Lets move forward and today with AIS .... better radars with automatic plotting etc. Fine - so the modern day OOW has become a Radar Baby ... and relies more heavily on tech ... but no matter what you do with a ship - it still does not stop on a sixpence, it still takes ages to turn, it still is a big lump of metal that really does not want to do what you want it to .... engines do not like being 'throttled' ..... cooling intakes cavitate if you hard over .....

On that last one - I can relate a true story that involved me.

Proceeding west after loading out of Nigeria. 300,000 ton tanker ..... the usual route was to run west clear of the oil fields and fisherman in dugouts ... till you could turn NW still about 50 miles off .... then hit the longitude line to run north to Las Palmas for Heli ops ...
There's me - 3rd Mate and on 4-8 watch ..... myself an old brit AB. Its early evening and sun setting ... its a brilliant clear day and that sun is BRIGHT !! I couldn't see a thing ahead.
Master was old school and like many old school believed in switching off Radar once you cleared away .... so there's me basically blinded by sun ... both radars and the awful early version KH Collision Avoidance screen off.
AB's is giving me stick moaning that Ch. Mate has cut overtime on board .. I'm trying hard to ignore and keep a watch ...

Speed 14kts ... course 280 ... then while out on stbd bridge wing - I get impression of something there but I'm blinded by the sun ...
Ignoring I may be mistaken - I :

1. Run in and Hard a starboard wheel .... this is really dangerous on a steamship at full away speed - the cooling water intake is on stbd side and immediately cavitates - engines shut down ... boiler overloads and all safetys lift !!
2. I grab phone while holding wheel over and call E/R .... KEEP THAT FU***** ENGINE GOING >>>

As that ship ... remember this is a fully laden 300,000 ton Tanker ..... turns and believe me that turn was the longest few minutes of my life ... I start to see the silhouette of a Reefer Ship all white ... pass so f*******g close across my bow ... as she passes - I swear to this day there was no-one on the bridge .......

Once it was clear we had missed her ... helm was eased ... I called E/R and apologised and asked if all OK ... they said no problem and I put her back on course ....

I couldn't understand why the AB had been so quiet throughout this till I realised the Master was standing in the doorway watching ... half out of sight.

Well 3rd Mate ... what shall we say eh ?? Bet you will never forget that will you ...

No need for me to shout or moan ... you've learnt a lesson that no-one could ever teach in a classroom ...

Yes Sir ... I'm sorry .....

No need be sorry lad ..

That Master and I from that day for some reason had a strange bond and understanding. I sailed with him twice and although I made some mistakes - he never hauled me out ...

But back to that ship ... on a later trip up to Europoort we were full loaded and coming into Dover straits making the double dogleg Cap Grisnez .... AB on the wheel ... I'm doing the nav ... Master with the Con.
Half mile to run Sir next course xxxx ..... Master gives order to Helm - who freezes !!
We both notice and Master grabs wheel - I run out on bridge wing and zap zap zap bearings ... back in ... OK Sir we can still make same course xxx ....
Relief AB takes over helm ... Master gives a long breath out !! I think about changing pants !!

Thank you 3rd Mate ... lets get her to Europoort !!

The vessel was the ST Linga ....

 

[zoidberg]

So it's not just mil aircrew who have some 'high heart rate' moments.....

 

[capnsensible]

So it's not just mil aircrew who have some 'high heart rate' moments.....

On the bright side though, its not long before you are home for tea and stickies.

 

[Uricanejack]

Ha Ha Ha.

I was often, told to turn the radar off, “so as not to wear it out“ .
I would try and point out, turning it on and off, all the time wears it out even quicker,
Fortunately, “Sparky” could ussualy fix it when a valve or tube would eventually blow.

I expect this particular myth and practice has died out.
Still requires someone to look at it occasionally