Couple of Practical OpenCPN Questions or Possibly Feature Requests

[Dockhead]

Originally Posted by conachair

Works fine on a win10 laptop and a raspberry pi this end....



Sample of a transmitted APB message.. (not the same as the gif above but similar method)

1,2,3 ,4,5,6,7 ,8, 9 ,10, , 11 ,12,13 ,14
$ECAPB,A,A,0.715,L,N,V,V,125.195,T,003,72.992,T,72 .992,T*38
$ECAPB,A,A,0.000,L,N,V,V,73.076,T,003,73.007,T,73. 007,T*05




( And Rick, will get round to making a few more gifs soon )

OK, maybe I'm doing something wrong. Will try again.

[transmitterdan]

Originally Posted by Moo

From the manual.



The last part is wrong I believe. The autopilot functionality and course steered is not affected, or should not be affected. The autopilot will be steering towards the next waypoint from the vessels current position, if it is in route following mode, rather than just steering a heading. So zeroing cross track should not affect the autopilot course steered at all.

It is not wrong. If you want to stay on the original route then don't use the Zero XTE feature. Let the XTE drive the pilot back to the original route.

Zero XTE works by creating a new straight line to the next waypoint. Thus the XTE immediately becomes Zero. Many chart plotters implement the same feature in the same way.

[rgleason]

This thread has been active! Thanks for reviewing the changes and discussing the XTE functions everyone.

First I hope we can find agreement on how it works and that it does work.
Then I'd like to make the statement clearer.

Moo advises the manual states:

Zero XTE only shows in the right click menu if there is a cross track error. When selected it resets the present XTE (Cross Track Error) back to zero. “Zero XTE” is useful if you are offset from the route and want the autopilot to follow a direct course adjusted for your current position, rather than the position of the last route waypoint.

TDan restates:

If you want to stay on the original route then don't use the Zero XTE feature. Let the XTE drive the pilot back to the original route.

Zero XTE works by creating a new straight line to the next waypoint. Thus the XTE immediately becomes Zero. Many chart plotters implement the same feature in the same way.

Can the first statement be made clearer in some way?

Thanks so much! Rick

[rgleason]

Moo:

I agree that being able to reset XTE is essential. It works for me on W10 with OCPN 4.8. Easy test:
Right click a point and chose "navigate to here"
Right click anywhere on the chart but NOT on the route "Zero XTE" should be there.

Small difference, but we need to create a cross track error to have it appear:

Easy test:
Right click a point and chose "navigate to here" to create a new Active Route.
Right click at some point off of the Active Route and pick "Move boat here" to create the cross track error.
Right click anywhere on the chart but NOT on the route "Zero XTE" should be there.

This is a great example for new users that should be the manual. Conachair has provided an very good illustration using this technique.

Now I have a question about Conachair's

Sample of a transmitted APB message.. (not the same as the gif above but similar method)

1,2,3 ,4,5,6,7 ,8, 9 ,10, , 11 ,12,13 ,14
$ECAPB,A,A,0.715,L,N,V,V,125.195,T,003,72.992,T,72 .992,T*38
$ECAPB,A,A,0.000,L,N,V,V,73.076,T,003,73.007,T,73. 007,T*05

Are the ECAPB sentences transmitting the XTE error to the Autopilot, in my case an nmea0183 in port? Such that when we check the Options > Connections > Network type connection and then check the "Output on this port as Autopilot or Nmea repeater" with an ID for the Talker?

Also what is the top line of digits 1 through 14?

Thanks again!

PS Conachair, I used your gif in the documentation, it works when the reader clicks on the image! See Modify a Route
https://opencpn.org/wiki/dokuwiki/do...modify_a_route
Do you guys think this is going to be OK? Having to click? I hope so.

Thank you. http://gifrecorder.com/

[transmitterdan]

Rick,

Reset XTE to zero means that the existing route leg is modified by resetting the start point to the GPS position at the moment the Zero XTE option is selected. This has the effect of changing the route leg from its original start point to the present ship position (and thus XTE becomes zero). Thereafter it will try to navigate a straight line from this new position to the next waypoint in the route. It is nothing more complex than that.
Zero cross track error does not change anything about the stored route. The original waypoints are not changed. Zero XTE only makes a temporary change to the start point of the present leg.

Does this make sense?

[bcn]

And this is why Conachair modifies the first waypoint in order to provoke a non-zero XTE in his animation.

Remember: only with XTE =/= 0 you can zero it. The other would not make any sense and therefore no "zero XTE" contextual menu exists in that moment.

[conachair]

Originally Posted by rgleason

Now I have a question about Conachair's

Are the ECAPB sentences transmitting the XTE error to the Autopilot, in my case an nmea0183 in port? Such that when we check the Options > Connections > Network type connection and then check the "Output on this port as Autopilot or Nmea repeater" with an ID for the Talker?

The ECAPB sentences are from these settings ->
with output filtered to "Transmit sentances - APB"


The I used node-red to look at what was being sent on that port.

Also what is the top line of digits 1 through 14?

Thats what each field is in the sentence, the forum formatting messes it up so theres an image below where hopefully it makes a bit more sense.

Thanks again!

PS Conachair, I used your gif in the documentation, it works when the reader clicks on the image! See Modify a Route
https://opencpn.org/wiki/dokuwiki/do...modify_a_route
Do you guys think this is going to be OK? Having to click? I hope so.

Thank you. Create Gif screencasts using the Gif Recorder

[transmitterdan]

If the autopilot is steering the boat based on a route downloaded by OpenCPN then O might not be driving the autopilot. If the boat's electronics is using the route points from O then that system is generating the XTE data and not O. O will send XTE messages to the AP when it is navigating a route as evidenced by the "highway" dashboard shown on the O chart display. If you don't see the highway dashboard then O is not driving. You can see the XTE value on one of the blocks in the highway dashboard.

[rgleason]

Originally Posted by transmitterdan

Rick,

Reset XTE to zero means that the existing route leg is modified by resetting the start point to the GPS position at the moment the Zero XTE option is selected. This has the effect of changing the route leg from its original start point to the present ship position (and thus XTE becomes zero). Thereafter it will try to navigate a straight line from this new position to the next waypoint in the route. It is nothing more complex than that.
Zero cross track error does not change anything about the stored route. The original waypoints are not changed. Zero XTE only makes a temporary change to the start point of the present leg.

Does this make sense?

TDan. Yes I does make sense. May I use it?

Conachair's gif demo shows moving the "start point" that is moved, I had not realized that, and used a different way to separate Ship position from the Active Route in order to create "Non-zero XTE" using "Move boat here" command which does create a "ZeroXTE" choice just like Conachair's technique.

I guess there are several ways to create the ZeroXTE choice.

[rgleason]

TDan wrote.

1. If the autopilot is steering the boat based on a route downloaded by OpenCPN then O might not be driving the autopilot.
2. If the boat's electronics is using the route points from O then that system is generating the XTE data and not O.
3. O will send XTE messages to the AP when it is navigating a route as evidenced by the "highway" dashboard shown on the O chart display. If you don't see the highway dashboard then O is not driving. You can see the XTE value on one of the blocks in the highway dashboard.

This is also helpful explanation. #3 will not work without an autopilot connected to Opencpn and receiving nmea out APB signals as Conachair shows.
[Is this correct?]

See
https://opencpn.org/wiki/dokuwiki/do...o_an_autopilot

This page seems to cover most of it.

[Moo]

Originally Posted by rgleason

Moo:
Small difference, but we need to create a cross track error to have it appear:
This is a great example for new users that should be the manual. Conachair has provided an very good illustration using this technique.

Not here I don't.. Zero XTE is available immediately without generating any XTE.. there might be XTE in cm but it reads 0!

[Moo]

Originally Posted by transmitterdan

It is not wrong. If you want to stay on the original route then don't use the Zero XTE feature. Let the XTE drive the pilot back to the original route.

Zero XTE works by creating a new straight line to the next waypoint. Thus the XTE immediately becomes Zero. Many chart plotters implement the same feature in the same way.

Yes OK some do, some don't.

But if the pilot was capable of steering the route and had been steering there would be no XTE. So this this situation is when you have a route active but have not been navigating it using the pilot (or your pilot can't cope), or you have dodged an obstacle.

I understand fully what it does. I just don't think the sentence makes sense especially the last phrase. Busy now I'll think about it whilst flying tomorrow.

[transmitterdan]

Moo,

How,do you think chart plotters make XTE Zero?

[transmitterdan]

Originally Posted by rgleason

TDan. Yes I does make sense. May I use it?

Conachair's gif demo shows moving the "start point" that is moved, I had not realized that, and used a different way to separate Ship position from the Active Route in order to create "Non-zero XTE" using "Move boat here" command which does create a "ZeroXTE" choice just like Conachair's technique.

I guess there are several ways to create the ZeroXTE choice.

The "move boat to here" selection creates a route with one leg. After that it is no different than running a route with multiple legs. So Zero XTE works there as well.

[transmitterdan]

Originally Posted by Moo

Not here I don't.. Zero XTE is available immediately without generating any XTE.. there might be XTE in cm but it reads 0!

I have read the source code. The XTE has to be non-zero else the option to zero it will not appear.