Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 14-07-2013, 19:18   #931
Registered User

Join Date: May 2009
Location: Massachusetts
Boat: 40' Silverton Aftcabin with twin Crusaders
Posts: 1,590
Re: Freighters vs. Sailboats

Quote:
Originally Posted by cappy208 View Post
There is more than just the A to Narragansett lanes. There is the A to Buzzards Bay lanes. In addition, there are 'recommended 'Deep Draft' lanes, which go all the way from the Race to Cleveland ledge (Buzzards Bay), all the way around BI, and cross (at right angles) the A to Narragansett lanes.

There are several of these 'Recommended' lanes on the east coast. Penobscot Bay ME has one. There is one off New Jersey Coast. One at the entrance to Delaware Bay, One in Chesapeake Bay, Thimble shoal channel. Give me time and I can probably remember more.

My point is, MANY people are out boating, and sadly many many many of them NEVER take out a chart to have a look at what is around, beneath and over them. Everyone has myopia. They only look at what THEY need or want to do (regarding the ocean) There is a larger responsibility to protect your, your family, your guests and most importantly MY life.

Although you have never said it, do you rely ONLY on chart plotters for your navigation information??? I have seen NO chart plotter (either in Raster or Vector) that gives ALL the 'real' chart info.

Personally I use paper charts all the time. Sure, I have my GPS on but I have never plotted courses with it. Got used to paper before I could afford a Loran years ago.




Quote:
Originally Posted by goboatingnow View Post
Foggy, that's fine , and in one to one , open seas , most sailors simply stay well clear , only a fool in a small boat attempts to assert stand on with a big freighter.

bUT , where you have multiple targets , and they are all sorting out how to pass each other , you may simply not have an option to " GET OUT OF ALL THEIR REACHES " , now you have a dilemma, what do you do.

Dave
Dave--

I presume there are places as you describe, maybe New York for instance around here. But a port such as Boston rarely has the conditions of multiple radar targets that consist of large freighters or transports. Where you sail, conditions I read about such as in the English Channel, things could be quite active.

Earlier posts in this thread discussed rules and so forth expecting large ships to yield to sailboats is/was just plain ludicrous.

Foggy
__________________

__________________
foggysail is offline   Reply With Quote
Old 14-07-2013, 19:24   #932
Nearly an old salt
 
goboatingnow's Avatar

Cruisers Forum Supporter

Join Date: Jun 2009
Posts: 13,649
Images: 3
Quote:
Originally Posted by conachair View Post

Can't speak for the Med but in my experience well offshore Atlantic they generally do, usually well before they appear over the horizon. A benefit of a steel radar reflecting hull
The only time I had it happen on a reliable basis was sailing with a AIS transponder.

Dave
__________________

__________________
Check out my new blog on smart boat technology, networking and gadgets for the connected sailor! - http://smartboats.tumblr.com
goboatingnow is offline   Reply With Quote
Old 15-07-2013, 04:47   #933
Registered User

Join Date: Sep 2012
Location: New England
Boat: Prairie 29
Posts: 201
Re: Freighters vs. Sailboats

Quote:
Originally Posted by goboatingnow View Post
Explain ?

Dave
Freighters vs. Sailboats
__________________
cappy208 is offline   Reply With Quote
Old 15-07-2013, 05:12   #934
Nearly an old salt
 
goboatingnow's Avatar

Cruisers Forum Supporter

Join Date: Jun 2009
Posts: 13,649
Images: 3
Quote:
Originally Posted by cappy208 View Post
None of those self referenced posts explain why the AIS plot on a chart plotter is inferior to the data directly from the AIS which is what you commented on.

Dave
__________________
Check out my new blog on smart boat technology, networking and gadgets for the connected sailor! - http://smartboats.tumblr.com
goboatingnow is offline   Reply With Quote
Old 15-07-2013, 05:15   #935
Registered User

Join Date: Sep 2012
Location: New England
Boat: Prairie 29
Posts: 201
Re: Freighters vs. Sailboats

ALodesman: I finally figure out why I didn't like your post using 'fine on the bow'. You are trying to make an 'all encompassing' comment, to make it 'easier' to explain (when discussing collision avoidance). This can't be done. The specific reason I am picking on your sentence is you use the phrase 'fine on the bow'. I have always understood that this term 'fine' is an 'interpretive one'. What is fine to you may not be fine to me. Now you want to throw out an ambiguous term onto a forum that is being read by newbies, who are going to develop poor judgement skills using this 'formula. ' Now, in addition to the 'fine on the bow' your theory depends upon same newbies using some imagined 'devining skills' to conjure up ship speed (to enter into the math equation)

When you are trying to solve a problem do you use the tried and proven answer, or do you make up a 'new' solution. Especially when that depends on introducing more guesswork into the equation? Why would you promote this new 'solution' to avoid collision to newbies?

I hear people saying these ambiguous terms all the time. When docking. When approaching a harbor. When rounding marks. People shout out 'It's fine on the bow'. I know from definition, a Point is 11.5 degrees. Fine is generally accepted to be between 'less than one point on either side of the bow' (any where in between) Even by your original description, at the 20/6 knot scenario, 'fine on the bow' is not correct either. (Even with somewhat of a definition!)

Also, there keeps popping up comments about how yachts have erratic courses.

During collision assessment, it is not specifically the 'other' vessels accurate course/speed. It is the aggregate course and speed over the duration of the encounter. Of course a constant speed/course is nice to be able to accurately predict, but if continually plotted, the relative motion line simply wanders but is fairly steady. (this is similar to the electronic relative trails on a RADAR screen.) I think you or Jackdale were discussing this and whether to install an actual Gyro abd to make your heading more accurate. Did you do that?
__________________
cappy208 is offline   Reply With Quote
Old 15-07-2013, 05:32   #936
Registered User
 
psneeld's Avatar

Join Date: Oct 2010
Location: Avalon, NJ
Boat: Albin 40 double cabin Trawler
Posts: 1,831
Re: Freighters vs. Sailboats

For info from USCG website....

10. Why have some AIS units stopped broadcasting valid position reports? On February 27th, 2008 the GPS constellation increased to 32 satellites (PRN 32) thus providing a 5% increase in satellite availability and DOP (dilution of precision) world-wide. It has come to our attention that some (non-USCG type approved) AIS units-particularly old equipment which is non-compliant with the GPS interface standard (IS-GPS-200)-cannot recognize this additional satellite and subsequently are unable to calculate a position and broadcast a valid AIS Position Report. Note, the reported malfunctioning units do continue to receive position reports and are able to send and receive AIS text messages. Owners of AIS equipment denoted here, however, should be aware that their internal GPS systems may not act as a proper-timing or position-back-up under certain circumstances, i.e. when in view of PRN32. AIS users must ensure their units have or are interfaced with a properly operating Electronic Position Fixing System at all times. GPS and/or AIS problems should be reported via the NAVCEN website or via phone to the USCG Navigation Information Service at 1-703-313-5900.
11. Why am I unable to see an AIS vessels' name or other static information (dimensions, call sign, etc.)? Shipboard AIS units autonomously broadcast two different AIS messages: a 'position report' which includes the vessels dynamic data (e.g. latitude, longitude, position accuracy, time, course, speed, navigation status); and, a 'static and voyage related report' which includes data particular to the vessel (e.g. name, dimensions, type) and regarding its voyage (e.g. static draft, destination, and ETA). Position reports are broadcasted very frequently (between 2-10 seconds-depending on the vessels speed-or every 3 minutes if at anchor), while static and voyage related reports are sent every six minutes; thus it is common and likely that an AIS user will receive numerous position reports from a vessel prior to receipt of the vessels' name and type, etc.
12. Why do I sometimes see more than one vessel with the same MMSI or vessel name (i.e. NAUT)? AIS users are required to operate their unit with a valid MMSI, unfortunately, some users neglect to do so (for example, use: 111111111, 123456789, 00000001, their U.S. documentation number, etc). A valid MMSI will start with a digit from 2 to 7, a U.S. assigned MMSI will start with either 338, 366, 367, 368, or 369. AIS users whom encounter a vessel using MMSI: 1193046 or named: NAUT should notify the user that their AIS unit is broadcasting improper data; see Nauticast AIS-MMSI Technical Bulletin for further information. All AIS users should check the accuracy of their AIS data prior to each voyage, and, particularly units that have been shutdown for any period of time. NOTE: If you are receiving (in range of) AIS reports from vessels using the same MMSI, they will appear as one vessel (jumping from position-to-position or line-to-line) on a graphical screen (e.g. ECS, ECDIS, radar) or on the AIS Minimal Keyboard Device (MKD).
13. I just purchased and installed an AIS Class B, will AIS Class A users ‘see’ me? Most should, but, soon all will. Although all Class A devices will receive Class B information; unfortunately, some older Class A models are unable to display this information on their Minimum Keyboard and Display (MKD) or may only have available the Class B vessel’s dynamic data (i.e. position, course and speed) but not its static data (i.e. vessel name, call-sign). Therefore, the Coast Guard cautions new AIS Class B users to not assume that they are being ‘seen’ by all other AIS users or that all their information is available to all Class A users. Further, we exhort users of certain AIS Class A units to, as soon as practicable, update their MKD’s and/or other external navigation display systems (e.g. Electronic Charts Systems, Electronic Chart & Display Information Systems, radar, etc.) in order to view this new stream of valuable AIS information that will enhance navigation safety and mitigate the risk of collision. A rulemaking to mandate such an update is forthcoming. Here is a listing of Coast Guard type-approved AIS Class A units which require a firmware update in order to display AIS Class B information.
__________________
psneeld is offline   Reply With Quote
Old 15-07-2013, 05:35   #937
Registered User

Join Date: Sep 2012
Location: New England
Boat: Prairie 29
Posts: 201
Re: Freighters vs. Sailboats

Quote:
Originally Posted by goboatingnow View Post
None of those self referenced posts explain why the AIS plot on a chart plotter is inferior to the data directly from the AIS which is what you commented on.

Dave
OK, I will try to make it clearer.

The information being transmitted by anyones AIS is all derived the same way. GPS imput.

What makes the data wrong (in relation to a chart plotter reference) is that the transmission rates change dependent on what kind of AIS one has, what the operating parameters are set to, and (this is probably the biggest part) antenna height and location.

Class A almost constantly transmits (when operating in the 'Underway' mode) Class A shifts down to around 3 minutes when you select 'docked, moored, or aground'

Class B only transmits from 3 seconds to 10 minutes depending upon whether underway or not.

The only time other vessels data will be completely accurate on YOUR chart plotter will be when YOU are completely stopped and They are completely stopped. The Data shown on a chart plotter will always be delayed as YOUR vessel moves over the chart plotter. So there is the error of your updated location, coupled with the other vessels 'delayed' info. This is not to say the info you are seeing is not fairly accurate, but it is time delayed.


Time and time again, I have seen yachts operating with their AIS showing them as 'moored', and they go flitting across the chart plotter in 'jumps' as their AIS updates. All because they forgot to change the operations to 'Underway.' But, you should change it to moored, or just shut it off when at a dock or mooring.


If you want proof of this, next time you are operating your vessel, while running along side another vessel with AIS, note how your position is not always right beside them. either you, or they jump ahead/lag behind. That is not data error, but AIS transmission delay induced error.

A quick Google search shows that Class A transmits at 12 mw. and Class B transmits at 2mw. The normal effective range of a class B is only 3 to 5 miles.

In this whole conversation, aren't we trying to see and be seen as far away as possible? Buy Class A ONLY.
__________________
cappy208 is offline   Reply With Quote
Old 15-07-2013, 05:54   #938
cat herder, extreme blacksheep
 
zeehag's Avatar

Cruisers Forum Supporter

Join Date: Jul 2008
Location: furycame alley , tropics, mexico for now
Boat: 1976 FORMOSA yankee clipper 41
Posts: 17,771
Images: 56
Send a message via Yahoo to zeehag Send a message via Skype™ to zeehag
Re: Freighters vs. Sailboats

sailing here on west coast of mexico, there are a few freighter only ports....unless there is a furycame coming, one is not to enter these ports.
when sailing south, there are many freighters headed not only into and from these ports, but to other places, near and far.
our job i s to avoid them and survive. survival means--keep out of their way--which is not difficult. even in 20 ft seas....
we were taught to take bearings constantly as we were taught to sail -- our teacher was a true captain, merchant marine. also rtw tallships and steamships.
is a shame more folks cannot learn to sail with these awesome folks who make learnng fun and knowledge special.
our guru taught us how to take bearings from our first time on boat, i was 7, my brother 6, with our eyes. is easy. too bad more souls cannot manage to do this.
even in seas, there is no way to not see a freighter....go uuuup, ye see him... into trough, dont see him... up on the crest, you see him;.etc....not difficult, and not rocket science.
there have been near misses at sea---the last i read of that involved a family was the melissa sue?? was yacht name. the freighter went out of its way--name was pan grace--to hit this sailboat in darkness, and most of family perished. this i sprinted and public record. the writings of the surviving soul, the mom, can be read.
when you see a freighter on ocean, is wise to avoid at all costs. same with shrimper and tug n tow, and other commercial traffic--they are enroute on business. we are messing about in boats. we can avoid them easily.
all we have to do is keep a proper watch. one doesnt need tools to watch. just eyeballs. learn what each side of a freighter looks like and watch em....as we drifted in the ocean approaching zihuatenejo, there were no fewer than 10 ships headed into and out o f lazaro cardenas port....they travel in many directions once they leave port. there is no designated shipping channel that we could see labeled on chart---but, as we are smart, we made sure to keep a good watch and AVOID the megaton monster of nightmares and dreams.
it isnt difficult..and there is, in usa, a 500ft safety zone around freighters, cruise ships and other commercial hugenesses that use ports and have limited maneuverability, thanks to the patriot act. that kinda over rules colregs. just stay away from big stuff and you are ok. start a space war and you will lose.
zeehag is offline   Reply With Quote
Old 15-07-2013, 05:55   #939
Registered User

Join Date: Nov 2007
Location: Probably in an anchorage or a boatyard..
Boat: Ebbtide 33' steel cutter
Posts: 3,538
Quote:
Originally Posted by cappy208 View Post


The only time other vessels data will be completely accurate on YOUR chart plotter will be when YOU are completely stopped and They are completely stopped. The Data shown on a chart plotter will always be delayed as YOUR vessel moves over the chart plotter.
That's a bit tricky to understand. Take opencpn as an example plotter, it receives a bit of data which says boat B is at position X, Y. It will plot that on the chart until some data arrives to say different or it times out, makes no difference what your GPS is saying or even if it isn't turned on, boat B is at Xdeg, Ydeg doing so many knots sog in such and such a cog. With data so many seconds old.
I can't see what difference your vessel can have on plotting the other ship. CPA obviously needs both data.
__________________
conachair is online now   Reply With Quote
Old 15-07-2013, 05:57   #940
Registered User

Join Date: Sep 2012
Location: New England
Boat: Prairie 29
Posts: 201
Re: Freighters vs. Sailboats

Quote:
Originally Posted by foggysail View Post
-

I presume there are places as you describe, maybe New York for instance around here. But a port such as Boston rarely has the conditions of multiple radar targets that consist of large freighters or transports. Where you sail, conditions I read about such as in the English Channel, things could be quite active.

Earlier posts in this thread discussed rules and so forth expecting large ships to yield to sailboats is/was just plain ludicrous.

Foggy
Scituate fishing vessel sinks in harbor after collision at sea - Scituate - Your Town - Boston.com

They're closer than you think!!!! People don't pay attention no matter where they are, and what they are doing.

You don't need multiple targets, just one will do!

It never happens? http://www.newburyportnews.com/x8457...-tragedy/print
__________________
cappy208 is offline   Reply With Quote
Old 15-07-2013, 07:02   #941
Registered User

Join Date: Sep 2012
Location: New England
Boat: Prairie 29
Posts: 201
Re: Freighters vs. Sailboats

Quote:
Originally Posted by conachair View Post
That's a bit tricky to understand. Take opencpn as an example plotter, it receives a bit of data which says boat B is at position X, Y. It will plot that on the chart until some data arrives to say different or it times out, makes no difference what your GPS is saying or even if it isn't turned on, boat B is at Xdeg, Ydeg doing so many knots sog in such and such a cog. With data so many seconds old.
I can't see what difference your vessel can have on plotting the other ship. CPA obviously needs both data.
You are correct. The data that you can get from the other vessel is whatever was transmitted last (well, at least the last time either you received it, or that it was transmitted) but the mention of the ICON on a chart plotter is what is suspect. The icon is related to the last place (XY) in relation to where your vessel was at the time of reception. If the other vessel does not update the position just hangs there until either you cancel out a 'lost target' or it times out.

I mention own vessel, because if you are moving, the relative position keeps changing as you move. If you are stopped, the relative position remains as accurate as is can be. Now, introduce a sporadic AIS target, and it gets even more inaccurate.
__________________
cappy208 is offline   Reply With Quote
Old 15-07-2013, 07:54   #942
Registered User

Join Date: Nov 2007
Location: Probably in an anchorage or a boatyard..
Boat: Ebbtide 33' steel cutter
Posts: 3,538
Quote:
Originally Posted by cappy208 View Post


I mention own vessel, because if you are moving, the relative position keeps changing as you move. If you are stopped, the relative position remains as accurate as is can be. Now, introduce a sporadic AIS target, and it gets even more inaccurate.
Though technically correct I've never seen it as a problem. The big boys are the ones where i find ais most useful, their signal seems reliable and regular. Certainly accurate enough to know a long way off if you need to really pay attention or can relax back to the kindle
__________________
conachair is online now   Reply With Quote
Old 15-07-2013, 08:06   #943
Registered User

Join Date: Sep 2012
Location: New England
Boat: Prairie 29
Posts: 201
Re: Freighters vs. Sailboats

Quote:
Originally Posted by conachair View Post
Though technically correct I've never seen it as a problem. The big boys are the ones where i find ais most useful, their signal seems reliable and regular. Certainly accurate enough to know a long way off if you need to really pay attention or can relax back to the kindle
Then you should see intermittent signals from the 'other' perspective! It is nice to see them, but when down to the nitty gritty, I would like to have a constant target. It's like RADAR. An intermittent target does wonders to boost doubt, while a steady solid target does wonders to boost confidence.
__________________
cappy208 is offline   Reply With Quote
Old 15-07-2013, 11:51   #944
Senior Cruiser

Cruisers Forum Supporter

Join Date: Nov 2005
Location: Out there doin' it
Boat: 47' Olympic Adventure
Posts: 2,635
Re: Freighters vs. Sailboats

Quote:
Originally Posted by cappy208 View Post
ALodesman: I finally figure out why I didn't like your post using 'fine on the bow'. You are trying to make an 'all encompassing' comment, to make it 'easier' to explain (when discussing collision avoidance). This can't be done. The specific reason I am picking on your sentence is you use the phrase 'fine on the bow'. I have always understood that this term 'fine' is an 'interpretive one'. What is fine to you may not be fine to me. Now you want to throw out an ambiguous term onto a forum that is being read by newbies, who are going to develop poor judgement skills using this 'formula. '
The term "fine on the bow" has only been in use for the last, oh, five hundred years or so. I've attached an excerpt from the Admiralty Manual of Seamanship, to help you come to terms with this simple concept. I don't think, given that it follows fairly closely with the dictionary meanings of the words, that the term is so ambiguous that newbies can't get the gist.

I'm not sure where you've got this idea that I've made up some all-encompassing rule. Quite the opposite - I'm trying to stomp out the all-encompassing 'point at his stern' advice. I've only illustrated why that won't always work, and have found myself trying to explain the basic principles of relative motion that are at play when a slow-moving vessel is in risk of collision with a fast-moving one, as might happen between a sailboat and a freighter, given as I thought that topical to this thread.

Quote:
Now, in addition to the 'fine on the bow' your theory depends upon same newbies using some imagined 'devining skills' to conjure up ship speed (to enter into the math equation)...
Why would you promote this new 'solution' to avoid collision to newbies?
I'm sorry, you've lost me. When have I done that?


Quote:
During collision assessment, it is not specifically the 'other' vessels accurate course/speed. It is the aggregate course and speed over the duration of the encounter. Of course a constant speed/course is nice to be able to accurately predict, but if continually plotted, the relative motion line simply wanders but is fairly steady. (this is similar to the electronic relative trails on a RADAR screen.) I think you or Jackdale were discussing this and whether to install an actual Gyro abd to make your heading more accurate. Did you do that?
I don't believe I was involved in that discussion. With ARPA the relative motion line bounces around whenever there's a change in input data - if your ownship speed and heading data are erratic, the RM will be erratic. The relative trail is an historic plot, that would give you an idea of the averaged - if you overlay your moving EBL on the trail, it would give you a steady RM line.
__________________
Lodesman is offline   Reply With Quote
Old 15-07-2013, 12:03   #945
Senior Cruiser

Cruisers Forum Supporter

Join Date: Nov 2005
Location: Out there doin' it
Boat: 47' Olympic Adventure
Posts: 2,635
Re: Freighters vs. Sailboats

Quote:
Originally Posted by conachair View Post
I'm not sure where the damping comes from but the little NASA unit I've used most seems to damp it well enough. The collision avoidance use is interesting, you could argue that a primary use of ais on small vessels is having sufficiently accurate data to ensure that a collision risk doesn't arise in the first place . Just a small course change can have you knowing you will cross a mile behind a ship which is still 5 miles away instead of cutting across it's bows. From experience ais is accurate enough for that.
Good to hear you have confidence in the data AIS is giving. I may well find I trust it enough, after I see it in action first-hand. Have you actually compared the AIS side-by-side with systematic radar plotting? Do you find the AIS plot is pretty accurate over time (assuming neither vessel needed to alter)?
__________________

__________________
Lodesman is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
The Timeless Elegance Of Multi Mast Sailboats In Photographs GaryMayo Monohull Sailboats 15 23-07-2012 23:30
Any Info About Northern Sailboats ? Snore Monohull Sailboats 10 27-03-2012 14:24
Easterly Sailboats easterly38 Monohull Sailboats 0 11-12-2011 14:02
Survey of Production Sailboats Under $50K BajaSurvey Commercial Posts 0 05-12-2011 17:18



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 10:50.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.