AIS Man Overboard Behaviour

[transmitterdan]

Originally Posted by transmitterdan

2) it seems that if you have the option checked to advance waypoint upon arrival then several things can terminate the route. For example, if the waypoint is within the arrival radius then the route is terminated. Or if the boat continues to move away from the MOB waypoint the route can be terminated automatically.

Correction: If navigating to a MOB waypoint the arrival never happens. I am still looking for how it creates multiple routes.

[transmitterdan]

Ok, I think I have gotten to the root of the problem.

There is a bug that only shows up when using VDR playback and the AIS MOB feature. When the VDR playback is finished the GPS status goes to invalid because there are no new position updates. But the AIS SART is still in the AIS list for some time longer.

When this happens O tries to initiate a navigate to the MOB waypoint. It first creates the waypoint in the waypoint database. Then it tries to create a route to that waypoint but that fails because the GPS isn't working (VDR has played out).

Because the create route failed it tries again thus creating yet another waypoint at the same coordinate. This continues forever creating an infinite number of MOB waypoints.

I will submit a pull request to fix this bug. But it only affects testers using VDR files. In a real MOB situation the GPS would be active and this condition should never occur in the wild.

[rgleason]

Additionally, If the boat location is not within the AIS Target List "Limit Range" the AIS-MOB-PLB will not alert. However as TDan points out there will be a route to the SART MOB created even if it is across the ocean labeled "Temporary AISMOB Route". This route is not active. See attached.

Before I was not getting this temporary route because I used VDRplayer, which keeps playing the SART-TEST.txt file so the route gets overwritten I think.

This time I used VDRplayer which runs the SART-TEST.txt file once, and the temporary route appears.

[rgleason]

TDan, This is a pretty complicated action, affected by a number of settings. I am not sure that is really what is happening. I think we should be checking this further to make sure the correction is indeed correct, and get some confirmation from others who are testing before making changes.

[rgleason]

Using VDRplayer and re running the nmea file SART-Test.txt, I get the alerts even though the boat is located in the US and the SART-MOB is in Europe.

This did not happen the first test using VDRplayer.

[rgleason]

Right click and activate the route.

[rgleason]

https://opencpn.org/wiki/dokuwiki/do...ttons:ais:sart

Once the alert is “Acknowledged”, the target behaves as any other AIS target. In the picture below the cursor is over the target. The SART target will persist on screen for 18 minutes after the last transmission irrespective of other settings for AIS. SART alerts always have priority over DSC and CPA alerts.

AIS SART messages and DSC distress calls are always found at the top of the AIS target list.

"If the AIS-PLB has a testing function that can be activated, there is a test mode whic uses a different icon."
(I would like to add this sentence above to the SART description. Is it ok, is it clearer?)

Testing It is possible to test a SART, to make sure it works.

Icon displayed when testing an AIS-SART device. ...Is green

[rgleason]

While waiting 18 minutes....
Here are Target Info and Wpt Properties.


TDan quote:

AIS SART with MMSI set as AIS MOB will drop a waypoint and it will start a "navigate to here" like route.

Don't you have to activate the route? The Temporary MOB route was inactive and I had to activate it.

Later: "Navigate to this" action actually Activates the Route and shows the Active Route box to the right. For me, the AIS-SART-MOB automatic action was only to create a "Temporary MOB Route" to the MOB and not activate it.

TDan quote:

Because the create route failed it tries again thus creating yet another waypoint at the same coordinate. This continues forever creating an infinite number of MOB waypoints.

I will submit a pull request to fix this bug. But it only affects testers using VDR files. In a real MOB situation the GPS would be active and this condition should never occur in the wild.

Using VDRplayer I didn't have this problem, (yet). I am wondering what was different...

[rgleason]

The AIS-MOB-PLB was reactivated and set off 9:19am .
The route was activated at 9:26am
The route was deactivated and deleted at 9:48am
The MOB is still listed as "Active" in the AIS Target List.
It is now 10:02 the MOB is still in the AIS Target List.

Added later:
AIS Target List - Limit Range setting
This setting appears to have no affect on MOB operations.
Which is fine IMHO.

I think we should have a VDR Test file for similuation of a "MOB Test" to see if the green icon appears.

[rgleason]

Here it is 10:15am.
Now the MOB appears to be gone from the AIS Target List
(This action should be double checked and confirmed!!!)
and the MOB is still showing on the chart.

I had checked for the MOB in the AIS Target List after 18 min had past and it was still there and showing as "Active". So I brought up "Target Info" where there is a selection for "Stop Tracking"... I hit that and the window stayed up and the selection changed to "Start Recording (track)". So that made sense to me.

Next I looked down and the MOB "Active" was gone from the AIS Target List, but the MOB waypoint was still on the chart.

[rgleason]

https://opencpn.org/wiki/dokuwiki/do...ttons:ais:sart

Questions:

1. Should the MOB waypoint on the chart disappear after 18 minutes too?

Or is that a precaution so that the MOB signal can leave a trail of breadcrumbs (waypoints) for the Rescue Team to refer to? I think that I would like to have all the AIS-SART-MOB waypoints kept because they are actual signals received, preferably with date/time stamps, perhaps numbering, and with the icon changed to some downgraded version in yellow or something.
Why? The track & times would be informative with regard to wind & current effects.

After 18 minutes the Icon should be changed to a downgraded, say orange or yellow version. Orange would show better I think.

2. "Navigate to here" feature which overrides the current route and sets up an Active route to the MOB. I am not sure we want this to occur if the ship is 4000 miles away and has absolutely not chance of getting to the MOB in time.
First of all, I believe this should certainly not occur if the MOB is further away than the AIS Target List > Limit Range Setting, and possibly some other setting dependent on boat speed etc.

3. Creation of a Temporary MOB Route (this action is explained in the Man Overboard section) which describes a completely Manually created MOB.
https://opencpn.org/wiki/dokuwiki/do...:man_overboard

Drop a Man Over Board Marker at your present position by pressing
* Man Over Board Button on the ToolBar. This button will always be furthest to the right among the buttons, for ease of finding.
or hit theKeys
*Ctrl + Space bar.

A mark, looking like the button is instantly created - the MOB mark.
The MOB mark will be called “MAN OVERBOARD at + time-stamp”

A temporary route, from a point 1 mile ahead on the current COG, and to the MOB mark is created and activated. On the screen, a course and bearing to the MOB mark will be displayed. This temporary triangular mark is labeled “1.0 NM along COG”.

I have not checked all of this action above. Have noticed most of it.

[QUOTE]
If COG, course over ground, is not available, no route is created but the MOB position is marked. This can happen if no GPS is connected, if the GPS signal is (temporary) unavailable or if the speed is so low that the GPS doesn't calculate COG.
[QUOTE]

This is what TDan is talking about. I am not clear on what change/fix he is proposing.

I have only gone through this once, really, and I think I and others should test these MOB actions at least several times, on different OS, first. Have a discussion and then maybe TDan would be kind enough to make the changes needed. I know Bdbcat and Pavel worked pretty hard to get this right! So our changes should be very deliberate and targeted, so as not to screw it up.

[transmitterdan]

The bug is a simple one. I should not attempt to create a route from own ship to a MOB alert if the own ship position is invalid. Presently it creates the MOB waypoint then it fails to create the route. So it keeps trying for as long as the MOB alert remains in the AIS list. Thus it creates hundreds and hundreds of waypoints if the own ship position is invalid. It should not create the way point if the route cannot also be created. It should keep trying so when the own ship position becomes valid then it will create the route.

You are right, it does not automatically activate the route. However, it does keep changing the route start point based on own ship position which is good.

The bug fix is trivially easy and will not break anything. I think this is all that's wrong.

[rgleason]

TDan, Ok, this sounds fine to me. How would I create a invalid ship position? Just so I could try it?

Also, does this address his concern:

I think we are talking at slight cross purposes here. The feature that I'm talking about is the Automatic MOB as described here: https://opencpn.org/wiki/dokuwiki/do...ual:toolbar_bu ttons:man_overboard

The idea being that if you have a crew member with a beacon on and it activates OpenCPN will recognise an AIS SART has gone off, check the MMSI number against your list of crew MMSI and if it is there it will automatically trigger a MOB like you had pressed "Space" cantered on the AIS position.

I think that every time a transmission is received it should trigger a new MOB at the new position. But what is happenening is that a single transmission is setting off multiple alerts and multiple MOBs all in the same place, and not navigating to them.

[transmitterdan]

The ship position becomes invalid when messages stop coming in from NMEA stream. So when the VDR file ends the ship position becomes invalid. But the AIS SART message is not purged so then you get lots and lots of MOB waypoints but no MOB route.

I cannot duplicate his other complaint. I would need a VDR file with numerous AIS SART pings. Preferably from a real scenario and not a manufactured data stream. I am interested in how O wades through all the typical NMEA data whilst handling a SART alert. Plus the stream has to run for about 30 minutes after the last AIS SART ping. So it will be a big file.

[rgleason]

So, we would need a real world file with a ships position during an entire SART event, with all the SART pings which would show the ships track and the MOB track over a period of time until rescue and deactivation, and then at least 18minutes (or perhaps 25 minutes more). A second case would be two SART MOB activations.

I made some changes to this page

https://opencpn.org/wiki/dokuwiki/do...ttons:ais:sart

It needs more clarification, I think.