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My chart plotter is Rosepoint Navigation Coastal Explorer running on an Intel NUC PC. I typically plot out a route before raising anchor and then activate the route. The chart plotter calculates Bearing to Waypoint and displays this on the instruments visible from the wheel. The helmsperson has a choice to steer to this course if wind allows, or steer a different course.
The helmsperson could engage the autopilot to steer a course using Compass or GPS mode. In GPS mode the autopilot controls for course over ground and corrects for current and leeway where Compass mode does not. NAV mode, where the helmsperson chooses to have the autopilot follow the course ordered by the chartplotter is different.
At the moment GPS mode is NAV mode if I change settings in the chart plotter to have it serve APB sentences to PyPilot but then I don't have GPS mode unless I go back to the chart plotter and disable APB sentences. If I have to choose I will almost never use NAV mode because though I know how to make these changes I don't want my crew (wife or other friends) messing around with those settings in the chart plotter. GPS mode is simpler and safer.
I would like both GPS mode and NAV mode selectable from the web browser interface to PyPilot.
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I would agree that an additional NAV mode would be a big improvement. I also prefer the GPS mode over the Compass mode for the reasons you mentioned. I got used to deactivating the entire plotter route altogether, as my own habit is to choose heading based on the plotter's COG predictor. But I do miss a simple bearing to waypoint then. So I would support this feature request wholeheartedly.
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Is NAV mode the same as GPS mode, except it ignores APB messages? In other words, it does not change the commanded heading, but otherwise identical? Would there be any other differences?
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2022-10-10, 09:17 PM
(This post was last modified: 2022-10-10, 09:26 PM by ironman.)
I take it opposite: that NAV mode would consume APB, while GPS mode does not. So when APB is offered, the GPS mode ignores it and simply maintains the commanded COG. The NAV mode, which should manually be selected, then would do what currently the GPS mode does: take the APB heading as commanded heading. If in NAV mode, and the APB messages stall, it should stay in NAV mode and follow the last commanded heading.
By the way, what PeterBro3 dubs 'NAV Mode' is known in the Raymarine universum as 'Track Mode'. This, however, conflicts with the OpenCPN parlour, where a 'track' is a recording of actual positions, and a 'route' is the thing that you want to follow. So, as not steer into confusion, I'd concur with 'Nav Mode'.
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I communicated via email with Sean before posting this thread and he used the term NAV mode which makes sense to me. I guess it could be Route mode because in this case the autopilot is following a route from the chartplotter. Rosepoint Coastal Explorer's help describes activating a route as Navigating a Route so either term could be used.
In answer to Sean, Ironman has it right, in GPS mode the autopilot steers to a fixed GPS heading. In NAV or Route mode it follows the APB course received from the chart plotter a GPS course over ground value and as the boat passes one waypoint the value changes and the boat changes course toward the next waypoint. A good question is what does NAV mode do when there is no APB value. In this case I think it should revert to GPS mode using the GPS course at the time it is started. If it stops receiving APB values while activated it should continue with the last value it received and maybe after a time revert to GPS mode.
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2022-10-11, 03:06 AM
(This post was last modified: 2022-10-11, 03:08 AM by seandepagnier.)
Sorry, yes I meant the opposite logic, where NAV does what GPS currently does, and GPS mode would just ignore APB.
Any other differences? even subtle ones?
It could certainly revert to GPS mode from NAV mode if APB is lost. In this cause, the typical logic could follow other modes and restore NAV mode when APB is restored.
The other option is to simply have NAV mode always available, but the advantage of it going away would be to indicate that pypilot is not receiving APB anymore, so this could be potentially useful. What is this about timeout? Do you mean it would go to GPS mode, then if APB is received again 10 minutes later it would no longer revert?
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There has to be a time limit for not receiving APB sentences after which it's considered a fault that needs to be addressed. I don't know how frequently APB sentences are sent, but assuming they are sent every few seconds then maybe 10 seconds without a sentence would be an error, or maybe it is five sentences not received is an error.
In my mind there are two alternatives.
A) just continue using the last APB sentence received and warn the helmsperson. If APB sentences are received again then follow the latest course received. This is probably easiest to implement.
B) switch to GPS mode and warn the helmsperson. If switching to GPS mode then I don't think I'd want to switch back to NAV mode if APB sentences are received again. I think that is a decision the helmsperson needs to make. This may be a safer approach.
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In both alternative you suggest "warn the helmsperson" but how exactly would that be done?
The watchdog plugin does support various ways to create an alarm from pypilot. If the second option is implemented, then the N on the screen would switch to G.
One downside is, if the autopilot is in GPS mode and the route is activated, it would not follow it until NAV mode is selected which would be an extra step. Currently you can activate/deactivate the route to switch it on and off, where this logic of a separate mode requires more user input. I think having an option to have gps and nav mode separate could work, as an optional setting.
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My other autopilots beep when they have an error such as they can't bring the boat to the ordered course. I guess TinyPilot does not have a sound alarm output and maybe this is something to be considered. Does TinyPilot send any error messages to OpenCPN?
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The watchdog plugin for opencpn can be configured to add pypilot alarms. The alarms can be configured for many different possible pypilot conditions as well as output a sound.
Alternately the watchdog plugin can give an alarm if the course is wrong which has nothing to do with pypilot and only requires gps or heading.
The pypilot hat can beep, but generally is not used for failing to hold course, this could be improved. I researched and considered adding a speaker output, but there is no good way to include the speaker inside of a box near the compass sensors and also be a loud enough speaker.. It is not worth compromising compass readings.
I am considering adding a sound output option to the web interface, so other devices like a phone/tablet or anything connected to pypilot this way could also produce audible alarms.
