Do we need/want an AIS filter?

[rgleason]

Dueling Ships in seas, reducing repeat alarms
-------------

rgleason:

2. Reduce nuisance alerts FS#807 - Add damping factor adjustable seconds of continued alert conditions before the alert sounds -not implemented

Paul Elliott:

For what it's worth, NavMonPc has a fixed filter that reduces the chance of transient CPA/TCPA alarms. In my first implementation I had no damping and I would generate alarms as vessels were turning and temporarily creating a CPA/TCPA condition. I now have fairly slow filters with hysteresis that have essentially eliminated this problem. They aren't adjustable, but I haven't personally found this to be a requirement. I don't recall the exact timing, but it's probably about five seconds. I don't consider Rate of Turn in my filtering, but that might be a good idea.

RooieDirk:

However for those who do use alarms, a small delay in raising an alarm when there is a course change of the target or of your own ship, could be useful.

Dockhead:

The main problem of alarm clutter is from vessels maneuvering in channels, where they are turning or will turn. Then you will get invalid alarms. The other main problem with alarm clutter is changing CPA horizon in different situations. One or two miles CPA and 30 minutes TCPA, say, which is totally appropriate in open water, will produce a constant stream of alarms in coastal waters. But the answer to this is not suppressing alarms, but setting up different criteria, for what is an alarmable collision risk, in different situations.

Existing feature reduces visual alarm clutter, retiring old alarms.
Check - Enable Target alert Acknowledge Alarm timeout (min) <--Have acknowledge alert first, then it times out.
http://opencpn.org/ocpn/ais

Another idea: Shut off a specific ship's alarm for a short period. (this is what timeout does, but maybe we could double click on the ship and turn it off for the timeout period.

Or Add a button to the Alarm Acknowledge button "Cancel thiis ship alarm for _X__minutes"

3. AIS Alarm acknowledge shortcut FS#1260 Provide a shortcut key + left mouse to close one or all Acknowledge alerts that are outstanding. -Not implemented, but does have Target Alert Acknowledge Timeout (min)
4. Temporarily Disable Alarms FS#1573 - Provide an Icon Button toggle to temporary stop all acknowlege alerts. - not implemented
Provide audible alarm instead (option) -Has audible alrm checkbox

[rgleason]

Rooie Dirk:

I'm playing with the idea of coding an AIS filter. Special in crowded areas the screen can be to clogged to be usefull.
Filtering could be done for CPA, TCPA, class B, class A .......
The filtered targets could be still visible but smaller, transparent or without AISname.
A warning should be onscreen, something like is used for "overzoom".
Maybe there should be a timer that switches off the filter after a certain amount of time.

RooieDirk Have you used this setting for Harbors or Coastal scale?
I just found it.

"Check - Show AIS Targets Real size"

Perhaps your Ship declutter tool should be used at Coastal scale and real size at Harbor scale.

Or perhaps as the ships get closer together, the ships should be shown at real scale so that skipper has better sense of avoidance tactics.

[rgleason]

Ship Declutter

Check - Show AIS Targets Real size"

The ship outline shows up when you have zoomed in quite a lot. Scale 820.
Therefore I think RooieDirk's Ship Icon declutter will work fine.


Alarm Repeats - dueling ships
AIS already has a pretty good tool for eliminating repeat Alarms from dueling ships that have to be acknowledged repeated times.

Existing feature reduces visual alarm clutter, retiring old alarms.
Check - Enable Target alert Acknowledge Alarm timeout (min) <--Have acknowledge alert first, then it times out.
AIS | Official OpenCPN Homepage

I did not find any reference in the documentation for an alarm dampener, but I would like to suggest that the existing Alarm Timeout is is exactly the user adjustable Alarm Acknowledge Timeout (dampener) that we need.

I set the timeout to 2 min and ran Hakefjord.txt and it worked quite well.

The only improvement I would like to see is to allow this Alarm Timeout to be applied to individual ships in another way, by right click on the Target, and select Alarm Timeout.

[rgleason]

AIS | Official OpenCPN Homepage
Look under AIS Data Port
There are four AIS icons which indicate different states
AIS alive
AIS alive & active There is AIS activity
AIS supressed only indicates target suppression is activated -alarm & display anchored/moored ships is suppressed in the AIS menu.
AIS alarm There are active alarms
AIS X ais disabled Any of the above buttons will toggle to this one. Turns off AIS alarms and display.

This is good, and the only thing missing I think is the ability to have and select settings for Ocean, Coastal and Harbor as suggested by Dockhead. RooieDirk's Shiip Declutter can be applied to Coastal and Harbor, I believe, and the "Show real ship" selection will still work and be useful at much smaller scales.

How could we implement Ocean, Coastal and Harbor settings?

[rgleason]

Alarms
2. Reduce nuisance alerts FS#807 -DONE. Add damping factor adjustable seconds of continued alert conditions before the alert sounds -This has been implemented with a user adjustible alam acknowledge timeout.
3. AIS Alarm acknowledge shortcut FS#1260- Could be implemented or closed - We do have Target Alert Acknowledge Timeout (min)
4. Temporarily Disable Alarms FS#1573 - Could be implemented or closed
5. The only improvement I would like to see is to allow the Alarm Timeout to be applied to individual ships in another way, by "Right Click on the Target, and select Alarm Timeout."

Ship Clutter
1. Rooie Dirk Ship Declutter Tool

Ease of Use in different conditions

Ocean, Coastal and Harbor settings
Ability to set and select for Ocean, Coastal and Harbor as suggested by Dockhead. RooieDirk's Shiip Declutter can be applied to Coastal and Harbor, I believe, and the "Show real ship" selection will still work and be useful at much smaller scales.

Dockhead what would your preferences be for Ocean, Coastal and Harbor?

[conachair]

Originally Posted by Dockhead

AIS alarms are also exceptionally valuable to draw your attention, in crowded waters, to one target out of possibly hundreds which suddenly apears on a collision course with you.

Class B has been mentioned, and (IMHO) being able to set different alarms for class A & class B would be very useful. Class B, I find, are often too erratic and unpredictable to pay too much attention to any alarms. Fishing boats do their own thing and yachts tack and gybe. It's the big boys we need to know about while they are still a way off, smaller boats you can dodge easier at closer range when you know better what they are up to.

[Dockhead]

Originally Posted by rgleason

Dueling Ships in seas, reducing repeat alarms
-------------

rgleason:
Paul Elliott: RooieDirk: Dockhead: Existing feature reduces visual alarm clutter, retiring old alarms.
Check - Enable Target alert Acknowledge Alarm timeout (min) <--Have acknowledge alert first, then it times out.
AIS | Official OpenCPN Homepage

Another idea: Shut off a specific ship's alarm for a short period. (this is what timeout does, but maybe we could double click on the ship and turn it off for the timeout period.

Or Add a button to the Alarm Acknowledge button "Cancel thiis ship alarm for _X__minutes"

3. AIS Alarm acknowledge shortcut FS#1260 Provide a shortcut key + left mouse to close one or all Acknowledge alerts that are outstanding. -Not implemented, but does have Target Alert Acknowledge Timeout (min)
4. Temporarily Disable Alarms FS#1573 - Provide an Icon Button toggle to temporary stop all acknowlege alerts. - not implemented
Provide audible alarm instead (option) -Has audible alrm checkbox

Interesting, but I think some of these measures are too fiddly. Very interesting for experimentation and development, but not so good by themselves for real life use.

When you're navigating in crowded waters, you don't want to be fiddling with anything. You want a quick shortcut to preset parameters which will make the system behave in a way appropriate to the situation.

[rgleason]

Dockhead:

Interesting, but I think some of these measures are too fiddly...not so good by themselves for real life use.

..navigating in crowded waters.. a quick shortcut to preset parameters which will make the system behave in a way appropriate to the situation.

I think we agree with you, how would you implement the settings and initiate the change in settings?
How do you like Conachair's idea and how would you include it?
-Shortcut keys? -Rotating Toolbar AIS Settings Icon? -Ocean, Coastal, Harbor or multiple user defined and named Ais settings? What is necessary?

Conachair:

..being able to set different alarms for class A & class B would be very useful.
Class B, ..too erratic and unpredictable to pay too much attention to any alarms. ..smaller boats you can dodge easier at closer range when you know better what they are up to.
Class A ..It's the big boys we need to know about while they are still a way off.

[Dockhead]

Originally Posted by rgleason

Dockhead:
I think we agree with you, how would you implement the settings and initiate the change in settings?
How do you like Conachair's idea and how would you include it?
-Shortcut keys? -Rotating Toolbar AIS Settings Icon? -Ocean, Coastal, Harbor or multiple user defined and named Ais settings? What is necessary?

Conachair:

Yes, I think Conachair's idea is perfect, and user-definable presets would be great, and a "rotating toolbar AIS settings icon" would probably be the perfect interface tool.

I agree with Conachair about alarms for Class "B", but I would suggest that not disabling alarms for Class B targets, but allowing us to define the alarm parameters differently, would be the thing. In open water, I, personally, use 1 or 2 miles CPA (2 miles when far offshore) and 30 minutes TCPA, as my alarm threshold. It would be great to be able to set different parameters for Class B targets, say a few cables and 10 minutes. In coastal waters, both Class A and B would be proportionally less.


One other random thought concerning moored vessels -- yet another reason, besides those already stated, not to filter these targets, is that it is not at all rare to encounter ships underway with their navstatus set wrong. It would suck to miss a ship underway on a collision course with you, just because it was falsely broadcasting "moored" as its navstatus.

[rgleason]

Is Class A and Class B the right way to separate large ships from smaller?
Class A SOLAS vessels of 300GT on international voyages
Class B Non-SOLAS Private boats less than 300GT, aimed at lighter commercial and leisure markets

300GT ship is about 140' or 43m

Found a wessel on the net with GRT=297
Length: 142.33 ft (43.38 m)
Breadth: 35.0 ft (10.67 m)
Draft: 10.042 ft (3.06 m)

OK what settings would you like? For example.

Ocean Settings
Class A = CPA 2 nm TCPA 45 min No CPA calc > 20nm
Class B = CPA 1.5 nm TCP 20 min No CPA calc > 5nm
RooieDirk Ship Declutter Tool=OFF
Ship names displayed. =ON
Suppress alerts for Anchored/Moored speed max .2 nm. = ON
Enable target alert acknowledge timeout 2 minutes =ON
Play sound on CPA/TCPA alerts =ON

Coastal Settings
Class A = CPA 1 nm TCPA 20min No CPA calc > 10nm
Class B = CPA 0.5 nm TCPA 15min No CPA calc > 5nm
RooieDirk Ship Declutter Tool=ON
Ship names displayed on chart.=OFF
Suppress alerts for Anchored/Moored speed max .2 nm. =OFF
Suppress alerts for Anchored/Moored speed max .2 nm. =OFF
Enable target alert acknowledge timeout 2 minutes =ON
Play sound on CPA/TCPA alerts =OFF

Harbor
Class A = CPA 1.5 nm TCPA 15 min No CPA calc > 7nm
Class B = CPA 0.5 nm TCPA 10 min No CPA calc > 2nm
RooieDirk Ship Declutter Tool =ON
Ship names displayed on chart.=ON
Suppress alerts for Anchored/Moored speed max .2 nm. =ON
Enable target alert acknowledge timeout 1 minutes =ON
Play sound on CPA/TCPA alerts =ON

How to change settings quickly?
Toolar Icon Button (rotating)

[chouliha]

We have been using OpenCpn for a number of years now and feeding it AIS data from our Vesper Marine 850. We have found the filters in the vesper marine Watchmate 850 to be excellent. First it gives you the option to set 4 main filters (offshore, coastal, harbor, etc) within these main categories you have the choice of numerous subfilters. This is really the best of all as you can quickly setup the unit for harbor with totally different filters than say offshore. Each category has been set with different settings. Easily switching between the major groups all your settings are saved.

For example being able to exclude anchored vessels. Approaching Panama Canal we had over 130- 140 vessels showing up but what I was really concerned with was those underway. Switching to harbor setting that I had preprogrammed eliminated those at anchor and made things much easier for me. I was still concerned with the ships at anchor but since I could see them and avoid them it was not a critical piece of information for us at the time.

BTW during this time our OpenCpn view with AIS on was almost solid AIS targets.

Sorry not adding. to the discussion but wanted to point out that the Watchmate units do have filtering and might want to be checked out before you design a new approach.

Kind regards

Chuck
Jacaranda
Marquesas





www.jacarandajourney.com

[rooiedirk]

Is Class A and Class B the right way to separate large ships from smaller?
Class A SOLAS vessels of 300GT on international voyages
Class B Non-SOLAS Private boats less than 300GT, aimed at lighter commercial and leisure markets

It is even worse. Her in NW Europa all ships (inland) over 20m length need to have a class A

[rgleason]

OpenCPN has an "Enable Target Alert Acknowledge Timeout ___ min"
I realize now this is different than a "Alert Damping factor ___min (w decimals)", so that it takes a few seconds of continued alert conditions (based on own boat heading and speed) before the alert sounds as requested in FS#807

I think "Alert Damping factor ___min (w decimals)"
would be a good way of helping to reduce repeats a little.

[rgleason]

FS#1575 Icon to enable/disable CPA Alerts

CPA alerting is usually annoying in/around harbours. To disable it, you need to go to the toolbox, AIS, disable checkbox.
Add an icon to the toolbar to enable / disable.
Alternative (to save space): use the 'show targets' icon to cycle between no targets, only targets, targets-with-warnings. Icon needs to show the current 'mode' in this case.

FS#460 Use Show Targets Icon to cycle alarm states.
Add an icon to the toolbar to enable / disable.
Alternative (to save space):
use the 'show targets' icon to cycle between
-- no targets shown,
-- only targets shown,
-- targets shown-with-warnings.
Icon needs to show the current 'mode' in this case.

2. FS#807 Add damping factor adjustable seconds of continued alert conditions before the alert sounds.
Different than "Enable Target Alert Acknowledge Timeout ___ min" which reduces repeat alarms after one has been issued.

[rooiedirk]

2. FS#807 Add damping factor adjustable seconds of continued alert conditions before the alert sounds.
Different than "Enable Target Alert Acknowledge Timeout ___ min" which reduces repeat alarms after one has been issued.

A little smarter approach would be better I think.
If an alarm comes up:
Check if there was a course/speed change of the target, if yes wait (if TCPA is not very low) until the next transmission of target.
Check for an ownship course/speed change, if yes wait untill course/speed is settled again.

I think this should do a better job then only wait for a fixed period of time