Cruisers Forum

Join CruisersForum Today

Thread Tools Search this Thread Rate Thread Display Modes
Old 05-01-2018, 11:04   #1291
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Helsinki (Summer); Cruising the Baltic Sea this year!
Boat: Cutter-Rigged Moody 54
Posts: 24,090
Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA

Originally Posted by rgleason View Post
Yes, Dirk's algorithm is not (T)CPA but is a blended and prioritized filter which "Attenuates less important targets" (makes them smaller) to help declutter the screen.
I was thinking of a similar, but additive indicator of the most critical targets, using a similar process.

I think you are both suggesting that (T)CPA settings are what should be used, however we have many users that are complaining that those alerts go off all the time in very crowded situations, basically because small boats bounce around and don't have as stable instruments, so I was trying to find a good way to provide better information to those user by using Dirk's algorithm.

We have some nmea recordings of these AIS situations (start of a race) which are a good example of what happens in these situations.
Let's consider separately the case of alarms, versus the case of "attenuation", bolding, coloring, etc.

Alarms are simply not useful in cases where you are in crowded pilotage waters with vessels following channels and fairways and often coming on to momentary collision courses. Alarms are just meaningless in such situations, so just turn them off. The purpose in my opinion of a collision avoidance alarm is to call your attention to the screen when you are in more open water and not watching the traffic constantly. In crowded pilotage waters you simply don't need it -- your eyes are on the screen anyway.

Highlighting targets in some way -- even if it's a momentary situation which triggers it -- is no problem in my opinion. Let the flash red as they turn across your path -- I'd like to know about that actually. And go black again as they continue turning. Also attenuating them -- let them be un-attenuated if they turn in a way which causes a momentary conflict. What problem is that? I think it's actually good to see them.

It would be useful to be able to set the criteria for alarms separately from the criteria for visual indicators.

It might be nice to have some kind of super-highlighting for a target which seems especially dangerous -- CPA/TCPA criteria PLUS maybe fulfilling those criteria for a longer period of time, and/or stricter criteria like 10 minutes and 0.5 miles (for example) instead of 30 minutes and 1 mile (for example. Red flashing icon and/or a separate audio alarm. That would be great. That is the only feature I don't already have and would like to have.

"Parce que je suis heureux en mer, et peut-Ítre pour sauver mon ame. . . "
Dockhead is offline   Reply With Quote
Old 05-01-2018, 13:53   #1292
Registered User
rgleason's Avatar

Join Date: Mar 2012
Location: Boston, MA
Boat: 1981 Bristol 32 Sloop
Posts: 12,554
Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA

Thanks Dockhead. That's very useful.

rgleason is offline   Reply With Quote
Old 08-01-2018, 16:01   #1293
Registered User
Juho's Avatar

Join Date: Apr 2015
Location: Finland
Boat: Nauticat 32
Posts: 838
Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA

Originally Posted by Dockhead View Post
Let's consider separately the case of alarms, versus the case of "attenuation", bolding, coloring, etc.
I think one could develop an alarm system that could be useful also in crowded environments. I don't have much experience on what would be practical since I don't have AIS, but in theory this could work.

The basic idea is that there could be alarms e.g. when some new vessel seems to be more dangerous or about equally dangerous as the current most dangerous vessel is. This would be combined with bolding and colouring. I might tune the system so that after the first alarm (based on CPA and TCPA) the system would focus on the (max) three most dangerous vessels (that meet the original CPA and TCPS criteria), display them accordingly (highlighted), and give alarms (maybe not so loud) when there is something new to be noted. These new things to be noted could be e.g. "the most dangerous vessel has changed" and "new vessel in the top three". There would be some hysteresis in the system, and memory of the past given alerts and their timing, to avoid unnecessary alerts due to variation in the measurements and other minor changes in the environment.

Juho is offline   Reply With Quote


Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
Challenge: Collision Avoidance! Pelagic Challenges 53 18-08-2017 19:54
CARD Collision Avoidance Radar Detector multihullsailor6 Marine Electronics 12 27-12-2015 20:12
Collision Avoidance - Tsunami Debris rreeves Health, Safety & Related Gear 22 03-05-2012 07:23
Collision Avoidance in Mexico: AIS or Radar or ? no_bad_days Pacific & South China Sea 27 19-09-2011 15:40
Distance to Horizon & Collision Avoidance GordMay General Sailing Forum 7 19-06-2009 00:18

Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 18:01.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.