AIS Functionality Definition

[PjotrC]

Originally Posted by bdbcat

13. AIS target speed/status discussion: I await a concensus. PjotrC, could you drive this ahead, please, perhaps as a separate thread?

Dave

I think Thomas summarized well the status quo and direction of changes:

Originally Posted by cagney

It all depends on where you are or what kind of navigation you are into!

So in my view, all the switches in the Toolbox are alright, with the exception of renaming anchored/moored (to "stationary/slow moving", addition mine, PjotrC), and make the AIS button dependent on that you actually use AIS ( a switch similar to Grib/Track).

But, ...there is definitely a need for a visual reminder of your settings in case some targets are suppressed. Hamish's suggestion and/or a different colour AIS button should work.

Thomas

If everybody agrees, in technical terms this would mean the following:

- In Tools->AIS there is a checkbox "Suppress stationary/slow moving targets" and a settable value for "Max stationary/slow target speed" (threshold default 0.3 kt)
- In Tools->AIS there is a checkbox "Suppress Alerts for stationary/slow moving targets"
- visual reminder for suppressing any part of AIS functionality might be a different icon, for example with a question mark added
- if there is no AIS input selected, no icon is shown
- the black ball on target means AIS status "at anchor or moored" AND sog<threshold (as implemented in 2.1.0)
- the functionality for suppressing display/alert for stationary/slow moving refers solely to SOG, not AIS status at all (change needed in 2.1.0)

Also, I was looking for small touches that would improve readability of crowded AIS displays. I think two are worth mentioning and proposing here. Both are trivial to implement (I have it in 1.3.6):

- when drawing targets, make two passes over the target list. In first pass draw slow targets (sog<=threshold), in second pass draw fast targets (sog>threshold). This ensures that a fast target will never hide beneath a slow one, and will be easy to select for properties dialog.
- when drawing cog predictor, draw the thin black predictor line on a thicker (3 pixels) background of the same colour that the target icon (green or yellow). It is almost invisible on the chart bacground, but helps a lot when targets overlap.

The sample "Partly Suppressed AIS" icon and some sample displays attached.

How about this?

Piotr

[LeaseOnLife]

Piotr

- In Tools->AIS there is a checkbox "Suppress stationary/slow moving targets" and a settable value for "Max stationary/slow target speed" (threshold default 0.3 kt)
- In Tools->AIS there is a checkbox "Suppress Alerts for stationary/slow moving targets"
- visual reminder for suppressing any part of AIS functionality might be a different icon, for example with a question mark added
- if there is no AIS input selected, no icon is shown
- the black ball on target means AIS status "at anchor or moored" AND sog<threshold (as implemented in 2.1.0)
- the functionality for suppressing display/alert for stationary/slow moving refers solely to SOG, not AIS status at all (change needed in 2.1.0)

YES! I am in agreement. The key for me is the last part: Alarm functionality must only rely on COG and SOG of a vessel.

[sinbad7]

I found an AIS target the other day with an indented stern in V shape.
It was a tugboat. Any explanation to this? Never seen targets other than the straight triangle shape.

[PjotrC]

The V-shape stern indicates a Class B target. Tugboats and pilot boats very often carry Class B transponders.

The other new symbology in 2.1.0 is:

- a black ball for vessels AT_ANCHOR or MOORED (suppressed when SOG exceeds the threshold)
- a single dash across for lost targets (was a cross underneath the icon in 1.3.6)
- a diamond with plus inside for NavAids

[la5zo]

My COMAR CSB200 Class B transponder will output ALR centences (AIS Alarm messages) that warns user about equipment/system failures.
Messages are time stamped and given a unique alarm number.

The ALR messages can be ACKnowledged by sending an ACK message.

Normally a MKD display would facilitate this. How about adapting these function to OpenCPN ?

And thanks for a great software !

Geir