Turn radius approaching route waypoing
Turn radius approaching route waypoing
April 29, 2018 08:19PM
I recently upgraded my auto pilot and now have everything linked via N2K network (laptop running Polar Navy, Simrad NAC-3, AP-48 control head, and VesparMarine XB-8000). Laptop accesses network via boat's WiFi network and talks directly to the XB-8000. Simrad AP gets route/navigation info via the XB-8000.

Just had a chance to spend the weekend doing sea trial setup for the new AP. After overcoming operator error (had never used PolarNavy for actual navigation before) boat will navigate an existing route, somewhat. However, it seems that PN doesn't have any way to sending turn info to the AP until the next waypoint line is intersected. Consequently, the AP will suddenly turn onto the new line to the next waypoint in the route, but has already advanced past the line so it is basically off-route and potentially putting the boat in danger (shallow channel sides, for example).

I've looked everywhere in PN to try to find a setting that would permit creating a turn radius (as I could do with my Garmin chartplotter when following a route) but can't seem to find any way to do that in PN. Other navigation programs have that functionality.

Any help with this? If it's not part of the software, it needs to be otherwise route navigation using PN is basically dangerous!
Re: Turn radius approaching route waypoing
April 29, 2018 09:26PM
There is no way to control the turn radius, nor is it really possible with the way autopilots operate.
NMEA0183 autopilot message allows external device to provide currently desired course (and, potentially, how far off track the vessel is). It is up to the autopilot to maintain this course. There is no provision to control the exact track taken - and trying to do so by adjusting courses repeatedly would result in "fighting against" the autopilot (aside from violating the standard and the expected data behavior).

I am not familiar with how Garmin chartplotter is integrated with autopilot, but it is most likely using its own proprietary communication mechanism that may provide a more fine grained control.

Note that a new segment begins when the current route point "arrival" occurs. You can control arrival mode (circle/distance or "perpendicular to course" ) as well as arrival distance, so that "arrival" occurs earlier than reaching the actual route point.

That said, it is explicitly a bad idea to rely on automatic route following anywhere where safety may be at issue, be that in confined or shallow waters or otherwise. PolarView is an information system first and foremost. I strongly urge you *not* to use it for autopilot management, and maintain full vessel control and appropriate watch at all times. This is also a product licensing requirement (in the EULA), aside from being common sense.

Polar Navy Support

Edited 2 time(s). Last edit at 04/29/2018 09:44PM by Polar Navy Support.
Re: Turn radius approaching route waypoing
April 29, 2018 10:33PM
I've been boating for almost 50 years. I understand safety and over-reliance on electronics. I don't need you to admonish me when I was asking a simple question and providing an example of how PN does not provide the same functionality as any number of other navigation programs (see Coastal Explorer as an example) and the consequences for anyone relying on the navigation functionality of PN when in a narrow channel or otherwise navigating in an area with a constraint on safe depths.

I'll try your suggestion re tweaking the arrival mode to see if that has any effect on when PN directs the AP to initiate a turn.
Re: Turn radius approaching route waypoing
April 29, 2018 10:59PM
Specifically to the question - upon "arrival" to the current route point, the next waypoint will be sent to the autopilot. This will happen when user selected arrival option is reached.
- In a circle/distance mode, "arrival" will be declared when vessel crosses a circle of specified radius around the route point (this circle is also shown on the screen)
- In a "perpendicular" mode, arrival will be declared when vessel crosses a line perpendicular to its course, drawn through the route point.

In either case, once "arrival" condition is matched, target route point is switched and the next route point is sent to the autopilot. Autopilot should turn to the new course and follow it based on its own internal parameters. That is - there is no external control of how fast autopilot will switch the course or what trajectory it will follow while doing so.

It is up to the user to ensure that the course as laid is free of any obstacles and arrival mode selected is appropriate for the given conditions. To do so, may require setting multiple route points to create a course to follow.

While I am not familiar with other products inner workings, it is unlikely that they are able to control the actual path the autopilot follows, as the protocol available to all software is the same and has no provisions for doing so. This is done explicitly to ensure that navigation software is *not* in control of actual vessel movement, and that any such movement is directly controlled only by the autopilot logic. FWIW, this feature is not referenced in their product documentation.

WRT product safety - unfortunately, reiterating safety basics is crucial. Your original post states that "using PolarView is dangerous". A software developer's greatest fear is a user who, rather than taking time to understand how software operates, applies it to control a large and expensive vessel with potentially dire consequences. Your reply is not very reassuring - while your confidence due to extensive time boating is appreciated, you did not understand how the product operates when you began using it. You also mention using the product for "navigation in a narrow channel", which is explicitly contrary to the previous advise of not using PolarView to control autopilot in confined waters.

This was the reason we were initially extremely reluctant to add autopilot control to the product - this was done upon multiple user requests. It may be time to retire this functionality entirely, if users are unable to use it safely. Do not take it personally, but the risk to the business our size is hard to overestimate.

At the very least, I would suggest starting by turning off autopilot NMEA 0183 sentence output in PolarView, and using it for extended period of time to only follow the route on the chart, while becoming well acquainted with how different arrival modes operate.

Polar Navy Support

Edited 2 time(s). Last edit at 04/29/2018 11:02PM by Polar Navy Support.
Re: Turn radius approaching route waypoing
April 29, 2018 11:09PM
Although discussing CE is off topic here, I would urge you to read the following thread: [www.coastalexplorer.net]

In particular, note the following reply from CE developers: "There is no relationship between the arrival circle radius and XTE. There is also nothing, aside from XTE precision in the Autopilot options, you can set (or would be possible to set) in Coastal Explorer that will impact how your autopilot behaves with respect to XTE."

I would suggest that, if you are using CE or any other navigation software to control the autopilot, you should take some time to learn more about its features and operation.

Polar Navy Support
Re: Turn radius approaching route waypoing
April 30, 2018 09:47AM
OK. Thanks for the informative response. Perhaps the "arrival circle" option is what I'm looking for. The AP needs some sort of input to tell it to start to turn before it arrives at the intersection of the two route lines.

I'll let you know if this is the solution, but it may be a few weeks before I get out again to test it.

Thanks, again.
Re: Turn radius approaching route waypoing
April 30, 2018 10:08AM
Is the "arrival" functionality set in the alarms/settings section? I can't find anything related to "arrival" anywhere else in PN. If so, the location is misleading, at least to me. I assumed everything in those two tabs (Alarms & Settings) related only to alarms; perhaps it would be helpful to include something to indicate that the alarm setting also affects navigation (in the way you explained).
Re: Turn radius approaching route waypoing
April 30, 2018 12:19PM
Yes, the arrival mode and distance is set in the "Alarms & Settings". "Arrival" status is first and foremost an alarm and only in some circumstances (exporting data to A/P) causes additional actions to be taken - hence its location in the alarm settings panel.

Note that you can select one of several modes of action upon arrival.
- In "automatic" mode next route point will be automatically selected once arrival condition is met.
- In "alarm dismiss" mode, alarm will appear (according to selected alarm mode), and next route point will be selected when alarm is dismissed by the user.
- Finally, "none" means that automatic advance of route point will not occur and user will need to change route point manually through the on screen navigation menu (accessible through context menu or by pressing key 'N' on the keyboard)

Polar Navy Support
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