Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 23-06-2008, 04:48   #1
Registered User
 
phiggins's Avatar

Join Date: Nov 2004
Location: Toronto, Canada
Posts: 1,288
Send a message via Skype™ to phiggins
AIS CPA/TCPA

To those of you who use AIS: what values do you set for the CPA and TCPA thresholds?

Thanks,

Paul
__________________

__________________
phiggins is offline   Reply With Quote
Old 23-06-2008, 06:31   #2
Senior Cruiser

Cruisers Forum Supporter

Join Date: Mar 2007
Location: Santa Cruz
Boat: Boatless Again
Posts: 4,314
On the open ocean I tell the crew to call me for any CPA of less than 5 miles.
__________________

__________________
donradcliffe is offline   Reply With Quote
Old 23-06-2008, 08:13   #3
Long Range Cruiser
 
MarkJ's Avatar

Cruisers Forum Supporter

Join Date: Dec 2007
Location: Australian living on "Sea Life" currently in England.
Boat: Beneteau 393 "Sea Life"
Posts: 12,828
Images: 25
Just so you dont leave the rest of us out of the discussion:

CPA - The Closest Point of Approach (CPA) calculation is performed if Fugawi is receiving your position from your GPS receiver. CPA is the distance you will be from an AIS vessel when you are nearest to it. The calculation is based on the current position, course and speed of your boat and each AIS vessel at the time of the last message.
TCPA - The Time to Closest Point of Approach (TCPA) calculation is performed if Fugawi is receiving your position from your GPS receiver. TCPA is the time (in minutes from now) at which your distance to the AIS vessel will be closest. The calculation is based on the current position, course and speed of your boat and the AIS vessel at the time of the last message. The TCPA will change when either vessel's course and speed are altered.
__________________
Notes on a Circumnavigation.
OurLifeAtSea.com

Somalia Pirates and our Convoy
MarkJ is offline   Reply With Quote
Old 23-06-2008, 08:24   #4
Registered User
 
phiggins's Avatar

Join Date: Nov 2004
Location: Toronto, Canada
Posts: 1,288
Send a message via Skype™ to phiggins
Thanks MarkJ. And usually programs like Fugawi and SeaClear make the two an AND condition. In other words for example , Sound an alarm if the target will pass within 1 mile within the next 15 minutes.

But evidently some programs and chartplotters make them an OR condition which to me doesn't make sense. Who cares about a target that will come within 1 nm but that won't happen for 4 hours.

Paul
__________________
phiggins is offline   Reply With Quote
Reply

Tags
ais

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
Best AIS? mestrezat Marine Electronics 6 13-11-2007 21:06
AIS 2xtreme Navigation 2 06-04-2007 17:49
Not new at all! AIS... Amgine Marine Electronics 1 03-12-2006 12:39
Hurricane Maximum CPA blahman Navigation 9 20-11-2006 18:49
AIS Receiver Curtis Marine Electronics 1 12-12-2005 08:28



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 13:31.


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.