route following - bug or expected behavior?

[Maes]

New OpenCPN user here, testing it as a possible alternative to some commercial software used at work. I noticed something odd on how OpenCPN 4.4 (for Windows) follows routes.

When following a route which uses the same waypoint multiple times, the route tracking will get 'confused' and inadvertently jump to the 1st 'loop' using said waypoint instead of continuing as per the route.

Ex. Route going through waypoints A -> B -> C -> D -> B -> E -> ...
Active tracked lines on OpenCPN will go A -> B -> C -> D -> B -> C -> D -> B -> C -> ...

Using 'activate next waypoint' follows the same loop issue instead of the proper sequence.

Could anyone confirm if this behavior is the same in previous versions? I'm currently at sea and relying on an absolutely horrid satellite connection so can't actually test with previous versions.

edit: I would normally have made this an entry on the bugtracker but it seems offline right now. I'm only getting "{"message":"Not Found"}" from the flyspray site.

[bdbcat]

Maes...

Sounds like a bug. Not tested, but I will investigate and report back.

OCPN can make the wrong choice if you start a route while ownship is already somewhere within the full lat/lon "envelop" of the route, depending upon your course at the time of activation. But this does not seem to match your scenario.

Thanks
Dave

[Maes]

Hi Dave,

This seems like a different issue, yes. It can be tested without a ship being involved at all. If a route is created with multiple passes through one waypoint, just activating the route and clicking 'Activate Next Waypoint' will show it gets stuck in the first loop going through the shared waypoint.

I have yet to see if stacking waypoints on the same spot and using a different element in the stack on each pass is a way to circumvent the issue (in theory it should), but it would be an inelegant fix at best.

Thanks,

Patrick

[Stu Jackson]

Originally Posted by Maes

I have yet to see if stacking waypoints on the same spot and using a different element in the stack on each pass is a way to circumvent the issue (in theory it should), but it would be an inelegant fix at best.

Dave, have you considered offsetting by a small distance a repetitive waypoint and using another name (WP1 and WP1a, for example)?

[boatbod]

I noticed this confused looping behaviour last week when I tried to reuse some waypoints in a route. It's definitely a bug, but I haven't put any time into attempting to reproduce it.

Sent from my SM-N920V using Cruisers Sailing Forum mobile app

[rgleason]

Originally Posted by Maes

Hi Dave,
... If a route is created with multiple passes through one waypoint, just activating the route and clicking 'Activate Next Waypoint' will show it gets stuck in the first loop going through the shared waypoint. ... see if stacking waypoints on the same spot and using a different element in the stack on each pass..

Thanks for stress testing. So why do you need to go in different kinds of circles? and through the same point multiple times - as in a forgetful lobsterman?

[Maes]

Originally Posted by rgleason

Thanks for stress testing. So why do you need to go in different kinds of circles? and through the same point multiple times - as in a forgetful lobsterman?

It's for seafloor mapping and sub-bottom analysis; for unusual seafloor features (faults, hydrothermal vents, underwater landslides, etc.) we repeatedly cross over said feature from different headings to get a better picture of the situation than doing just a single pass. It's also useful in case the exact coordinates aren't known or there is some imprecision in conversion, say with repeating old surveys originally done in what is believed to be NAD27 datum (but not 100% certain) while we now use WGS84.

As such, the goal isn't going through different kinds of circles, but going through the same point multiple times.

[boatbod]

In my case, the reason I did it recently was because we took a trip starting from an overnight anchorage then heading up-river to check out the sights before heading back down the river and onward to the "real" destination.