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-   -   Collision Avoidance, Cones of Uncertainty, and Appropriate CPA (https://www.cruisersforum.com/forums/f90/collision-avoidance-cones-of-uncertainty-and-appropriate-cpa-189919.html)

Pete7 03-10-2017 02:58

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by StuM (Post 2490889)
AAAAhhhhhhhhhh!

Even after all the discussions over the last few months, some still don't grasp the fundamental concept of COLREGs :banghead:

Could be worse, some folk call them "rules of the road" :rolleyes: I drove on the left hand side of the road on my way into work this morning and overtook by passing the car in front on his right hand side :wink:

Lodesman 03-10-2017 03:30

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by ramblinrod (Post 2491685)
Hmmm, the line of sight calculation depends on which on-line calculator I use, and seems to vary from 8 to 10 miles for both points being 12 ft above sea level.

Formula given earlier 1.17 x sq rt(HoE in ft). For 12 ft it's 4.05 miles. Since it's that for both objects, the range would be 8.1.

ramblinrod 03-10-2017 06:34

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by Lodesman (Post 2491759)
Formula given earlier 1.17 x sq rt(HoE in ft). For 12 ft it's 4.05 miles. Since it's that for both objects, the range would be 8.1.

But, but , but, I have seen other formulae, including...

line of sight dx =1.23 * h1^0.5 + 1.23 h2^0.5
sub h1 and h2 = 12
= 8.5

...and yet others that report up to 10 nm.

Relates to the old adage, a man with one clock knows exactly what time it is, while a man with two is never really sure. ;-)

(It seems, even with GPS time tied to atomic clocks this still holds true when some boats cross the finish line. Just sayin...

Lodesman 03-10-2017 08:31

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by ramblinrod (Post 2491823)
But, but , but, I have seen other formulae, including...

line of sight dx =1.23 * h1^0.5 + 1.23 h2^0.5
sub h1 and h2 = 12
= 8.5

...and yet others that report up to 10 nm.

Relates to the old adage, a man with one clock knows exactly what time it is, while a man with two is never really sure. ;-)

(It seems, even with GPS time tied to atomic clocks this still holds true when some boats cross the finish line. Just sayin...

You're using the formula for radar horizon.

ramblinrod 03-10-2017 09:31

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by Lodesman (Post 2491884)
You're using the formula for radar horizon.

hmmmm, could be, I've just tried about 20 different sites for on-line calculation based on the search "visual line of sight calculator". I have about 20 different answers, some radio, some visual.

Lodesman 03-10-2017 10:44

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
All you need is here: https://thenauticalalmanac.com/Bowdi...Navigator.html

El Pinguino 03-10-2017 14:19

Re: ~
 
Quote:

Originally Posted by Dockhead (Post 2491732)
To be precise, it's a section of a cone. The concept is plotting the accumulating uncertainty about the positions of moving vessels. It's analogous to the cone of uncertainty used in hurricane forecasts. See here:

https://en.wikipedia.org/wiki/Cone_of_Uncertainty

It's a powerful concept which is essential to extracting useful information out of imprecise data.

Well then , we really should be using correct terminology ( eg Cone of Uncertainty ) at all times so as not to cause confusion when discussing right of way issues...no?

ramblinrod 04-10-2017 08:13

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by Dockhead (Post 2491482)
Actually not luck, but the skill of the mariners on the bridges of ships you have encountered.

They generally assume that we have no idea what we are doing, and maneuver far ahead of an encounter with a WAFI. Their maneuvers are generally calculated to take them far enough away from us that no dumb sudden move we might make -- like a 90 degree turn, 1/4 mile away -- can cause a collision.

If you will talk to commercial mariners about collision avoidance, as I have, you will hear this story over and over again.

One of the really ingenious things about the COLREGS is that the system works and collisions will be prevented if even only one vessel understands what to do.

I am sure that there are many commercial mariners who wish there were no other vessels than the one they are in charge of on the water, and believe that everyone else out there is an idiot.

When one gets paid to do a job, they are likely to follow different procedures than one who is not. The one who is paid, must follow orders or direction of authority. The one who is not, just needs to satisfy their pucker factor.

I also know that some recreational sailors get way too anal about "proper vessel handling". For some, excessive obsession with collision avoidance and prudent seamanship may be "fun", for others, any more than required to not get sunk, is too much infringement on their freedom and relaxation.

I guess you fall into the former, and I fall in the latter category.

I would not go so far as to suggest either is right or wrong, just that it does take all kinds, to make the diverse boating community we all enjoy.

evm1024 04-10-2017 11:27

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by ramblinrod (Post 2492445)
I am sure that there are many commercial mariners who wish there were no other vessels than the one they are in charge of on the water, and believe that everyone else out there is an idiot.

When one gets paid to do a job, they are likely to follow different procedures than one who is not. The one who is paid, must follow orders or direction of authority. The one who is not, just needs to satisfy their pucker factor.

I also know that some recreational sailors get way too anal about "proper vessel handling". For some, excessive obsession with collision avoidance and prudent seamanship may be "fun", for others, any more than required to not get sunk, is too much infringement on their freedom and relaxation.

I guess you fall into the former, and I fall in the latter category.

I would not go so far as to suggest either is right or wrong, just that it does take all kinds, to make the diverse boating community we all enjoy.

I'm guessing that Canada is much the same as the US in that COLREGS are not optional. In the US the COLREGS and the treaties that require them are implemented in US Law. Mostly in 33 CFR.

Anytime a vessel ignores US Inland rules on internal US waters or COLREGS elsewhere they are breaking US Law.

I recall no occupation "recreation".

It sounds like you are saying that Commercial Truck Driver have to follow the driving rules but I'm a recreational driver so I don't really have to stop for a red light or yield when merging. So long as it does not exceed my pucker factor.

Contrary to what you state there is a right and a wrong. It is coded in Law.

A case in point - at my marina people sound their horn for 1/2 second (if we are lucky) when leaving their berth. But the law requires a prolonged blast (4 to 6 seconds).

Should there be a collision at that point they would be found substantially at fault because they did not give the warning blast as required by law -even if the other party was doing something stupid.

ramblinrod 04-10-2017 14:06

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by evm1024 (Post 2492559)
I'm guessing that Canada is much the same as the US in that COLREGS are not optional. In the US the COLREGS and the treaties that require them are implemented in US Law. Mostly in 33 CFR.

Anytime a vessel ignores US Inland rules on internal US waters or COLREGS elsewhere they are breaking US Law.

I recall no occupation "recreation".

It sounds like you are saying that Commercial Truck Driver have to follow the driving rules but I'm a recreational driver so I don't really have to stop for a red light or yield when merging. So long as it does not exceed my pucker factor.

Contrary to what you state there is a right and a wrong. It is coded in Law.

A case in point - at my marina people sound their horn for 1/2 second (if we are lucky) when leaving their berth. But the law requires a prolonged blast (4 to 6 seconds).

Should there be a collision at that point they would be found substantially at fault because they did not give the warning blast as required by law -even if the other party was doing something stupid.

I said nothing about not complying with Colregs or laws?????????

FWIW, in the marina we keep our rec vessel with about 230 others, I have never heard a single one sound a horn FOR ANY REASON.

evm1024 04-10-2017 14:23

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by ramblinrod (Post 2492445)
I am sure that there are many commercial mariners who wish there were no other vessels than the one they are in charge of on the water, and believe that everyone else out there is an idiot.

When one gets paid to do a job, they are likely to follow different procedures than one who is not. The one who is paid, must follow orders or direction of authority. The one who is not, just needs to satisfy their pucker factor.

I also know that some recreational sailors get way too anal about "proper vessel handling". For some, excessive obsession with collision avoidance and prudent seamanship may be "fun", for others, any more than required to not get sunk, is too much infringement on their freedom and relaxation.

I guess you fall into the former, and I fall in the latter category.

I would not go so far as to suggest either is right or wrong, just that it does take all kinds, to make the diverse boating community we all enjoy.

To me "proper vessel handling" includes following COLREGS/inland rules. You state that you are in the camp that "any more than required to not get sunk, is too much infringement on their freedom and relaxation"....

StuM 04-10-2017 15:14

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by ramblinrod (Post 2492445)
...
For some, excessive obsession with collision avoidance and prudent seamanship may be "fun", for others, any more than required to not get sunk, is too much infringement on their freedom and relaxation.

I guess you fall into the former, and I fall in the latter category.
...


Quote:

I said nothing about not complying with Colregs or laws
You certainly implied it. There is a lot more to COLREGs than "not getting sunk".

Your "right" to freedom and relaxation on the water ends at the point where it endangers others and that's when you don't follow COLREGs.

ramblinrod 04-10-2017 15:29

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by StuM (Post 2492667)
You certainly implied it. There is a lot more to COLREGs than "not getting sunk".

Your "right" to freedom and relaxation on the water ends at the point where it endangers others and that's when you don't follow COLREGs.

OK, I think some misinterpreted my intention.

I was referring to the infinite amount of effort one may apply to what they consider "prudent seamanship".

I believe everyone should follow colregs.

To me, that is the minimum requirement to not get sunk.

Colregs does not require any recreational boater (at least under a specified length) to even have AIS, or to plot courses using any specific protocol, nor to maintain any minimum distance from another vessel.

This is what I was referring to.

One can set up all the electronics wizardary at their nav station, and plot course changes 1500 miles in advance, so as to never get closer than 100 miles to another vessel, if they wish.

I don't wish to and colregs does not require it.

That is my point.

Colregs (and or any other applicable legislation) is the minimum; anything beyond that is a matter of personal pucker factor.

El Pinguino 04-10-2017 17:37

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by StuM (Post 2492667)
You certainly implied it. There is a lot more to COLREGs than "not getting sunk".

Your "right" to freedom and relaxation on the water ends at the point where it endangers others and that's when you don't follow COLREGs.

'Not getting sunk' really is the same as 'Preventing Collisions' as in 'International Regulations for Preventing Collisions at Sea' just expressed in a slightly different manner....

markpierce 04-10-2017 17:49

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by ramblinrod (Post 2492638)
I said nothing about not complying with Colregs or laws?????????

FWIW, in the marina we keep our rec vessel with about 230 others, I have never heard a single one sound a horn FOR ANY REASON.

That is pathetic. PATHETIC! Other than during high-tide, I sound a loud, four-second blast on my horn when leaving the marina which is surrounded by a sea-wall blocking the view. ... I do plead guilty in not usually sounding three shorts when backing out of the berth.


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