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Old 18-06-2014, 09:03   #406
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Re: Why Integrate the Autopilot ?

It is possible that one did not activate the XTE sentence during setup, I suppose. Then the warning to be careful that the installation does steer by XTE and not BTW would be sensible.

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Old 18-06-2014, 19:23   #407
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Re: Why Integrate the Autopilot ?

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Originally Posted by colemj View Post
It is possible that one did not activate the XTE sentence during setup, I suppose. Then the warning to be careful that the installation does steer by XTE and not BTW would be sensible.

Mark
NMEA0183 sentences are 'compound', meaning BTW & XTE are in the same sentence. Unlikely the UI gives the choice to not include XTE.

NMEA2000 has a separate PGN for XTE. Any worthy AP should fail to engage a 'track' if XTE is missing.
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Old 18-06-2014, 22:14   #408
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Re: Why Integrate the Autopilot ?

Hi Greg,
Hope you are still following your thread?
I thought you might be trying to find reasons why they need to be tied together.
Our Raymarine stuff usually worked well enough but once we found the autopilot not working but the goto on the chartplotter engaged the AP allowing us to continue comfortably.
Turns out the pod with the wind speed and AP head unit was full of water and had shorted the wifi unit for the smartpilot remote control. So mabye having them all conected was a blessing in this case.
See you on the water.
Derek
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Old 19-06-2014, 06:21   #409
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Re: Why Integrate the Autopilot ?

Quote:
Originally Posted by DotDun View Post
NMEA0183 sentences are 'compound', meaning BTW & XTE are in the same sentence. Unlikely the UI gives the choice to not include XTE.

NMEA2000 has a separate PGN for XTE. Any worthy AP should fail to engage a 'track' if XTE is missing.
In Coastal Explorer, for instance, one chooses the sentences it wants sent. APA, BTW, XTE are all separate choices.

Of course, so are APB and RMB/RMC, so I don't know why these wouldn't be used.

I was just pointing out that it was POSSIBLE that someone could set things up so that XTE wasn't sent. I don't know about whether an AP would engage without it.

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Old 19-06-2014, 08:16   #410
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Re: Why Integrate the Autopilot ?

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Originally Posted by colemj View Post
In Coastal Explorer, for instance, one chooses the sentences it wants sent. APA, BTW, XTE are all separate choices.

Of course, so are APB and RMB/RMC, so I don't know why these wouldn't be used.

I was just pointing out that it was POSSIBLE that someone could set things up so that XTE wasn't sent. I don't know about whether an AP would engage without it.

Mark
Admittedly, I don't have experience with more than 3 vendors APs, but I haven't found an AP that supports other than the compound sentences.

I agree that a lesser knowledgable type can mess things up at the UI. I would like to think AP designers would put failsafes in place such that when that happens (XTE missing), the AP would act differently (like refuse to accept the 'track').
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Old 19-06-2014, 16:07   #411
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Re: Why Integrate the Autopilot ?

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Admittedly, I don't have experience with more than 3 vendors APs, but I haven't found an AP that supports other than the compound sentences.

I agree that a lesser knowledgable type can mess things up at the UI. I would like to think AP designers would put failsafes in place such that when that happens (XTE missing), the AP would act differently (like refuse to accept the 'track').
I just looked at my Robertson (now Simrad) AP-20 manual. It just references XTE and BWW. I think that these two single items are all it uses, although you can send it the various compound sentences too. I expect that it just picks out these two bits of data. It does balk and announces NO VALID GPS DATA if it is not receiving this information. I believe that it will use BWW, the bearing from a current waypoint to a next waypoint, to intially point the boat in the desired direction. Then it appears to use XTE exclusively to make adjustments to stay on the course line. That is all it takes to correct for wind and current. The chart plotter will use additional bits to display heading, but the AP does not need it.
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