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Old 11-28-2022, 12:14 PM   #1
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Garmin chartplotter auto-guidance won't work with Simrad Pilot

Is it true that a 2019 Garmin Charplotter 94SV won't provide autoguidance to a 2019 Simrad Autppilot AP44?

Previous owner set up boat with Garmin chartplotter an simrad autopilot on the NEMA 2000 network. Devices see each other, but Garmin won't interface with the Simrad auto navigation function. Garmin sends no autoguidance data.

Garmin web site says their chartplotter won't support 3rd party autopilots.

Is this true? Is this day and age, Garmin still does this type of closed system? I am shocked.

Please tell me I'm wrong or this is a workaround.

Thanks.
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Old 11-28-2022, 02:43 PM   #2
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I suspect what they are saying is that you cannot control your autopilot from the Garmin MFD. They do have a support article describing this and that they do send GoTo and RouteTo information to third party autopilots.

https://support.garmin.com/en-US/?fa...Is0LGsUOfjHxC8

I have an older simrad ap (NMEA 0183) which can get next waypoint info from my furuno gear. I just need to accept then course change to the next waypoint on the AP.

BTW - in practice I don't use my AP for routing, I set a course myself.
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Old 11-28-2022, 02:49 PM   #3
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I suspect what they are saying is that you cannot control your autopilot from the Garmin MFD. They do have a support article describing this and that they do send GoTo and RouteTo information to third party autopilots.

https://support.garmin.com/en-US/?fa...Is0LGsUOfjHxC8

I have an older simrad ap (NMEA 0183) which can get next waypoint info from my furuno gear. I just need to accept then course change to the next waypoint on the AP.

BTW - in practice I don't use my AP for routing, I set a course myself.

That sounds right, and makes a lot more sense.
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Old 11-28-2022, 02:51 PM   #4
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I know my Garmin works with my Simrad AP, but only when following a "go to." For pre-planned routes with waypoints in them, apparently it uses proprietary NMEA sentences/PGNs which nobody else recognizes. What do you expect? It's Garmin!
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Old 11-28-2022, 03:59 PM   #5
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Garmin intentionally does not interface with non-Garmin hardware and software. Take a look at electronic charts. Garmin at one time accepted Explorer electronic charts for the Bahamas. But no longer.
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Old 11-28-2022, 04:08 PM   #6
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Looking more closely, Garmin talks about three types of autopilot steering control; Autoguidance which appears to be their version of auto routing, Go To which appears to be a standard go to waypoint, and Route Go which appears to be standard following of a route (sequence of waypoints).


Garmin says Autoguidance only works with their pilot, but that Go To and Route To will work with other pilots.


And as pointed out, you can't do control-panel type commands from the MFD for non-Garmin pilots. This is true for everyone's pilots. Unless you have same-brand pilot and MFD, things like pilot on/off, auto on/off, heading change, nav on/off are all controlled from the pilot control panel.
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Old 11-28-2022, 04:35 PM   #7
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I know my Garmin works with my Simrad AP, but only when following a "go to." For pre-planned routes with waypoints in them, apparently it uses proprietary NMEA sentences/PGNs which nobody else recognizes. What do you expect? It's Garmin!
Thank you for the replies. So if I set a waypoint and select "Go To" the bearing will be sent to the Simrad and the Simrad will follow the bearing? And will the autopilot then adjust should the GPS bearing to the mark change due to wind, current, chop etc.?
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Old 11-28-2022, 04:59 PM   #8
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And as pointed out, you can't do control-panel type commands from the MFD for non-Garmin pilots. This is true for everyone's pilots. Unless you have same-brand pilot and MFD, things like pilot on/off, auto on/off, heading change, nav on/off are all controlled from the pilot control panel.
I only recently learned this. Like the OP, I expected integration. I expected the brain functions to be within the MFD and it would simply send simple course/XTE sentances to the AP. At its core, an AP doesn't receive too much external information........or so I thought.

Peter
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Old 11-28-2022, 05:45 PM   #9
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In shopping for gear for a new build I came across that issue. Sorry, I didn't go with Garmin so I have no saved link to share.

As I recall it has to do with some proprietary calculation of the turning radius at a waypoint that can only be communicated to a Garmin autopilot.
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Old 11-28-2022, 09:20 PM   #10
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...So if I set a waypoint and select "Go To" the bearing will be sent to the Simrad and the Simrad will follow the bearing?

No. It will send cross-track error data to the autopilot, which will correct accordingly to keep you on a straight line to the "go to" point.



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Originally Posted by Hammer View Post
...And will the autopilot then adjust should the GPS bearing to the mark change due to wind, current, chop etc.?

Yes and no. It will strive to always keep you on that straight-line course. Obviously this is what you want if that course line is the only safe option. But if you get off course, say to avoid traffic, it'll snap you back over to your intended track, instead of just taking you from wherever you are to the end point.
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Old 11-28-2022, 10:01 PM   #11
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I only recently learned this. Like the OP, I expected integration. I expected the brain functions to be within the MFD and it would simply send simple course/XTE sentances to the AP. At its core, an AP doesn't receive too much external information........or so I thought.

Peter

Then I'm not sure I explained it well, because I think it's more like you thought.


Here's how an AP works in "Nav" mode, which is what you use to navigate to a single waypoint, or to follow a sequence of waypoints, aka a route.


On the MFD/chart plotter you "activate" the waypoint or route. It sounds like Garmin calls this Go To and Route To. Coastal Explorer calls it "activating a route". I don't recall what Ray, Simrad, or Furuno call it.


When a route is activated on the plotter, it starts sending a few message that are really very simple. It basically reports the bearing and distance to the next waypoint, the name of the waypoint, and the cross track error (XTE). All this is calculated by the plotter based on your current position, and gets repeated every second or two. When you first activate the route, the plotter creates an imaginary "track line" from your current position to the waypoint, and the XTE is just how far off the line you are at the moment to the left or right. The plotter doesn't know and doesn't care if anyone is listening. This part is universal across every plotter I've ever seen, and the messages are completely standardized both on 0183 and N2K.



Assuming the AP starts out in standby, you now need to put it in Nav mode. That is done at the AP control panel. This, plus switching to Auto mode, or back to Standby is what has to be done at the AP control panel, not the MFD.... Unless.... you have the same brand MFD and AP. In that case most of the MFD vendors allow you to change the AP mode via the MFD. Otherwise you need to use the AP control panel.


Once in Nav mode, the AP now starts listening to those waypoint and XTE messages coming from the plotter. The AP will then steer the boat to keep it on the track line with some degree of precision. If the boat drifts too far off to one side as indicated by an excessively large XTE, the pilot will start to steer the other direction trying to bring the XTE back down to zero. It's really a very simplistic system. It's liek two people driving a car. One person (the plotter) watches the road and continually calls out the car's distance from the guard rails. The other person (pilot) has the wheel but is blindfolded, and steers the car based on the distances from the guard rails called out by the first person. Their job is to never get to too close to either guard rail.



It's also important to understand that the pilot really never knows anything about the route. All it ever knows about is the current waypoint and XTE info it's getting from the plotter. People often talk about downloading a route to the pilot, and that can lead you to think it's sending all the route info to the pilot, but it's not. It only ever knows about one waypoint at a time. The last waypoint is forgotten and the next waypoint is unknown. When a route waypoint it reached, the waypoint that's being sent to the AP suddenly changes to the next waypoint. Once the AP sees the change, it turns towards the new waypoint, and starts trying to reduce the XTE to get the boat onto the new track line.


Once you realize that the AP's only mission in life is to stay on the track line, you will understand some of otherwise unexpected things that pilots all do. For example, let's say you go into Auto mode to maneuver past a boat, then switch back to Nav mode. You probably aren't still on the track line when you do that, and the AP will turn to get back to it. Depending on how far off you are, the turn can be very aggressive, and is the cause of a lot of Crazy Ivans, or other unexpected sudden turns.


There are a couple of ways to get back on track gracefully. One is to do a "Reset XTE" on the chart plotter. This causes the plotter to compute a new track line from your current position. After doing that, you are now back on the line with a zero XTE, and the pilot just needs to adjust your course so you are heading for the waypoint. You'll want to hit Reset XTE immediately before resuming Nav mode. Otherwise, if the boat isn't already heading towards the waypoint, you will be accumulating XTE every second and the pilot will try to correct for that. My preferred method is to steer in Auto mode until you are heading towards the waypoint, then hit Reset XTE, then resume Nav Mode. That puts you on heading and on track when you engage Nav mode, and the pilot should take over gracefully.


The other way is to steer back to the original track mode until you are back on track and on heading, then engage Nav mode. But unless you deviated pretty far from course or really need to be on the original track, I find the first method works best.


Sorry for the long post, but I think this is a real mystery for a lot of people when it's actually a really simplistic system. You can also dig into your pilot's manual to learn about variations on some of these modes. For example, some pilots have setting where it will always steer towards the waypoint and ignore XTE. That eliminates the issue of getting back on track after a diversion, but the boat will side slip off the track based on wind and current. In some cases this is fine, but in others it's not.
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Old 11-28-2022, 10:19 PM   #12
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Then I'm not sure I explained it well, because I think it's more like you thought.


Here's how an AP works in "Nav" mode, which is what you use to navigate to a single waypoint, or to follow a sequence of waypoints, aka a route.


On the MFD/chart plotter you "activate" the waypoint or route. It sounds like Garmin calls this Go To and Route To. Coastal Explorer calls it "activating a route". I don't recall what Ray, Simrad, or Furuno call it.


When a route is activated on the plotter, it starts sending a few message that are really very simple. It basically reports the bearing and distance to the next waypoint, the name of the waypoint, and the cross track error (XTE). All this is calculated by the plotter based on your current position, and gets repeated every second or two. When you first activate the route, the plotter creates an imaginary "track line" from your current position to the waypoint, and the XTE is just how far off the line you are at the moment to the left or right. The plotter doesn't know and doesn't care if anyone is listening. This part is universal across every plotter I've ever seen, and the messages are completely standardized both on 0183 and N2K.



Assuming the AP starts out in standby, you now need to put it in Nav mode. That is done at the AP control panel. This, plus switching to Auto mode, or back to Standby is what has to be done at the AP control panel, not the MFD.... Unless.... you have the same brand MFD and AP. In that case most of the MFD vendors allow you to change the AP mode via the MFD. Otherwise you need to use the AP control panel.


Once in Nav mode, the AP now starts listening to those waypoint and XTE messages coming from the plotter. The AP will then steer the boat to keep it on the track line with some degree of precision. If the boat drifts too far off to one side as indicated by an excessively large XTE, the pilot will start to steer the other direction trying to bring the XTE back down to zero. It's really a very simplistic system. It's liek two people driving a car. One person (the plotter) watches the road and continually calls out the car's distance from the guard rails. The other person (pilot) has the wheel but is blindfolded, and steers the car based on the distances from the guard rails called out by the first person. Their job is to never get to too close to either guard rail.



It's also important to understand that the pilot really never knows anything about the route. All it ever knows about is the current waypoint and XTE info it's getting from the plotter. People often talk about downloading a route to the pilot, and that can lead you to think it's sending all the route info to the pilot, but it's not. It only ever knows about one waypoint at a time. The last waypoint is forgotten and the next waypoint is unknown. When a route waypoint it reached, the waypoint that's being sent to the AP suddenly changes to the next waypoint. Once the AP sees the change, it turns towards the new waypoint, and starts trying to reduce the XTE to get the boat onto the new track line.


Once you realize that the AP's only mission in life is to stay on the track line, you will understand some of otherwise unexpected things that pilots all do. For example, let's say you go into Auto mode to maneuver past a boat, then switch back to Nav mode. You probably aren't still on the track line when you do that, and the AP will turn to get back to it. Depending on how far off you are, the turn can be very aggressive, and is the cause of a lot of Crazy Ivans, or other unexpected sudden turns.


There are a couple of ways to get back on track gracefully. One is to do a "Reset XTE" on the chart plotter. This causes the plotter to compute a new track line from your current position. After doing that, you are now back on the line with a zero XTE, and the pilot just needs to adjust your course so you are heading for the waypoint. You'll want to hit Reset XTE immediately before resuming Nav mode. Otherwise, if the boat isn't already heading towards the waypoint, you will be accumulating XTE every second and the pilot will try to correct for that. My preferred method is to steer in Auto mode until you are heading towards the waypoint, then hit Reset XTE, then resume Nav Mode. That puts you on heading and on track when you engage Nav mode, and the pilot should take over gracefully.


The other way is to steer back to the original track mode until you are back on track and on heading, then engage Nav mode. But unless you deviated pretty far from course or really need to be on the original track, I find the first method works best.


Sorry for the long post, but I think this is a real mystery for a lot of people when it's actually a really simplistic system. You can also dig into your pilot's manual to learn about variations on some of these modes. For example, some pilots have setting where it will always steer towards the waypoint and ignore XTE. That eliminates the issue of getting back on track after a diversion, but the boat will side slip off the track based on wind and current. In some cases this is fine, but in others it's not.
First, that's a great post TT. Basis of a good article.

Second, it's more or less how I figured APs worked. They are pretty simple - had to be because the functionality hasn't changed for at least 30 years.

I understand that difficulty in sending certain on/off/pause functions via a non-interfaced control, but, leaving aside the wisdom of auto-routing, why is an MFD-generated auto-route treated differently than a typical waypoint route? Only reason I can think of is a proprietary block on communicating for marketing purposes, but why do all OEMs restrict?

20+ years ago, at the dawn of rwcreqtioanl MFD creation, I used a laptop running Cap'n Voyager interfaced to my Comnav AP (0183 of course) with an A/B switch so I could select between my ancient GPS or the PC via a serial port. PC would always receive the GPS signal. I figured out pretty quickly how basic the comm sentences were.

Even though I went full Simrad, I opted for dedicated AP control heads. They were not that expensive, and I just didn't feel comfortable with AP controls getting buried on an MFD page

Thanks again for the great description.

Peter
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Old 11-29-2022, 03:33 AM   #13
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Originally Posted by twistedtree View Post
Then I'm not sure I explained it well, because I think it's more like you thought.


Here's how an AP works in "Nav" mode, which is what you use to navigate to a single waypoint, or to follow a sequence of waypoints, aka a route.


On the MFD/chart plotter you "activate" the waypoint or route. It sounds like Garmin calls this Go To and Route To. Coastal Explorer calls it "activating a route". I don't recall what Ray, Simrad, or Furuno call it.


When a route is activated on the plotter, it starts sending a few message that are really very simple. It basically reports the bearing and distance to the next waypoint, the name of the waypoint, and the cross track error (XTE). All this is calculated by the plotter based on your current position, and gets repeated every second or two. When you first activate the route, the plotter creates an imaginary "track line" from your current position to the waypoint, and the XTE is just how far off the line you are at the moment to the left or right. The plotter doesn't know and doesn't care if anyone is listening. This part is universal across every plotter I've ever seen, and the messages are completely standardized both on 0183 and N2K.



Assuming the AP starts out in standby, you now need to put it in Nav mode. That is done at the AP control panel. This, plus switching to Auto mode, or back to Standby is what has to be done at the AP control panel, not the MFD.... Unless.... you have the same brand MFD and AP. In that case most of the MFD vendors allow you to change the AP mode via the MFD. Otherwise you need to use the AP control panel.


Once in Nav mode, the AP now starts listening to those waypoint and XTE messages coming from the plotter. The AP will then steer the boat to keep it on the track line with some degree of precision. If the boat drifts too far off to one side as indicated by an excessively large XTE, the pilot will start to steer the other direction trying to bring the XTE back down to zero. It's really a very simplistic system. It's liek two people driving a car. One person (the plotter) watches the road and continually calls out the car's distance from the guard rails. The other person (pilot) has the wheel but is blindfolded, and steers the car based on the distances from the guard rails called out by the first person. Their job is to never get to too close to either guard rail.



It's also important to understand that the pilot really never knows anything about the route. All it ever knows about is the current waypoint and XTE info it's getting from the plotter. People often talk about downloading a route to the pilot, and that can lead you to think it's sending all the route info to the pilot, but it's not. It only ever knows about one waypoint at a time. The last waypoint is forgotten and the next waypoint is unknown. When a route waypoint it reached, the waypoint that's being sent to the AP suddenly changes to the next waypoint. Once the AP sees the change, it turns towards the new waypoint, and starts trying to reduce the XTE to get the boat onto the new track line.


Once you realize that the AP's only mission in life is to stay on the track line, you will understand some of otherwise unexpected things that pilots all do. For example, let's say you go into Auto mode to maneuver past a boat, then switch back to Nav mode. You probably aren't still on the track line when you do that, and the AP will turn to get back to it. Depending on how far off you are, the turn can be very aggressive, and is the cause of a lot of Crazy Ivans, or other unexpected sudden turns.


There are a couple of ways to get back on track gracefully. One is to do a "Reset XTE" on the chart plotter. This causes the plotter to compute a new track line from your current position. After doing that, you are now back on the line with a zero XTE, and the pilot just needs to adjust your course so you are heading for the waypoint. You'll want to hit Reset XTE immediately before resuming Nav mode. Otherwise, if the boat isn't already heading towards the waypoint, you will be accumulating XTE every second and the pilot will try to correct for that. My preferred method is to steer in Auto mode until you are heading towards the waypoint, then hit Reset XTE, then resume Nav Mode. That puts you on heading and on track when you engage Nav mode, and the pilot should take over gracefully.


The other way is to steer back to the original track mode until you are back on track and on heading, then engage Nav mode. But unless you deviated pretty far from course or really need to be on the original track, I find the first method works best.


Sorry for the long post, but I think this is a real mystery for a lot of people when it's actually a really simplistic system. You can also dig into your pilot's manual to learn about variations on some of these modes. For example, some pilots have setting where it will always steer towards the waypoint and ignore XTE. That eliminates the issue of getting back on track after a diversion, but the boat will side slip off the track based on wind and current. In some cases this is fine, but in others it's not.
OMG, TT, thank you for this primer, especially on the reset XTE. Forever, I have thought there was something wrong with the AP when I had to steer off course and then invoke back to the next waypoint. Yup, crazy ivans. I did figure out to manually steer back to the original course line and then go back to Nav mode.
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Old 11-29-2022, 06:49 AM   #14
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I understand that difficulty in sending certain on/off/pause functions via a non-interfaced control, but, leaving aside the wisdom of auto-routing, why is an MFD-generated auto-route treated differently than a typical waypoint route? Only reason I can think of is a proprietary block on communicating for marketing purposes, but why do all OEMs restrict?

Good question, and I really don't know. It doesn't surprise me that Garmin has done something proprietary with the autorouting feature to push people towards a one-vendor solution. That's Garmin's M.O. "creating value-add features to better serve our customers", translation, "lock-in features to better serve Garmin".



I agree with you that it's certainly not necessary. There is no reason why a computer generated route needs to be constructed or represented any differently from any other route, and I'll bet other companies automatically generating routes in a standard format. Coastal Explorer has a feature to automatically create "suggested routes", and in the end they are no different from any other route.


Buy hey, anyone who's interested in autorouting and considering Garmin is very likely to buy their autopilot to get the feature. It's the oldest trick in the book for tech products. Create proprietary "value-add" to lock in customers.
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Old 11-29-2022, 07:06 AM   #15
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OMG, TT, thank you for this primer, especially on the reset XTE. Forever, I have thought there was something wrong with the AP when I had to steer off course and then invoke back to the next waypoint. Yup, crazy ivans. I did figure out to manually steer back to the original course line and then go back to Nav mode.

There are typically a bunch of adjustments in the pilot that can help with this too. This will vary from pilot to pilot, but here are a few that I have seen.


Rate of Turn: This sets a rate of turn limit, and by reducing it you can limit the pilot to making slower, more gentle turns rather than hard turns that will toss dishes and drinks across the boat. I find 2-3 deg per second to be slow enough to be comfortable for boat occupants, but fast enough to make most waypoint turns without overshooting the new track line. If the turn is too slow the boat won't make the waypoint turn in time to land on the new track line. I have seen the default ROT limit be too high, resulting in very abrupt turns.


Return to Track angle: I don't recall the exact wording for this, and the only place I recall seeing it is in a Simrad AP70/AP80. It's the max re-approach angle allowed when returning to a track line. In the worst case, a pilot trying to return to a track line will make a 90 degree turn (perhaps very quickly based on ROT setting) to steer straight back to the track line, then another 90 degree turn onto the track line once back to it. This is the shortest and fastest way back to the track line, but the most abrupt and alarming to the boat occupants. Lowering this limit causes the pilot to approach the track line at a shallower angle rather than a hard 90 deg. The pilot will then steer back to the existing track line with a lot less drama.
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Old 11-29-2022, 07:40 AM   #16
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...... Coastal Explorer has a feature to automatically create "suggested routes", and in the end they are no different from any other route.
This sounds a lot like an auto-routing function that CE has resisted for years. I cannot find it - or have I misunderstood? While I'm thumbs-down on using auto-routes, they are useful for quick calculation of total distance for passage planning.

Thanks in advance -

Peter
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Old 11-29-2022, 08:04 AM   #17
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I run a garmin plotter and a comnav pilot. One thing I found is that you can send too many messages to the pilot if the installer just turned everything on. Iím still working on dialing in the routing functions, but a it is exactly like tt described except i havenít seen a reset xte function. Iíll have another look though, maybe I just missed it.
Iíd never use an auto generated route anyway, so that function is worthless to me . In fact, Im only playing with the the route to function for the heck of it. I donít really use it that way. Like many others I just point and shoot with the pilot.
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Old 11-29-2022, 08:26 AM   #18
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.... . In fact, Im only playing with the the route to function for the heck of it. I donít really use it that way. Like many others I just point and shoot with the pilot.
I assume you mean you use "AUTO" vs "NAV." AUTO maintains a heading- no XTE involved. So the boat is subject to set and drift when there are sideways forces of wind and current. NAV compensates by using XTE to keep you on a line snapped at moment NAV is activated.

When transiting a narrow channel, especially one without good visual reference points such a dredged channel where getting outside the channel means shallows, I find it helpful to set the GOTO (NAV) waypoint between the next channel markers to assure I stay within the channel. Better than gluing eyeballs to a highway view under AUTO.

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Old 11-29-2022, 09:52 AM   #19
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Vessel Name: Solstice
Vessel Model: Grand Banks 47 Eastbay FB
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Quote:
Originally Posted by twistedtree View Post
Once you realize that the AP's only mission in life is to stay on the track line, you will understand some of otherwise unexpected things that pilots all do. For example, let's say you go into Auto mode to maneuver past a boat, then switch back to Nav mode. You probably aren't still on the track line when you do that, and the AP will turn to get back to it. Depending on how far off you are, the turn can be very aggressive, and is the cause of a lot of Crazy Ivans, or other unexpected sudden turns.
Yup, that's excellent explanation.

I'll add that resetting XTE is fine... if you're in open water. If you're in a situation of limited depth, resetting XTE could cause real problems if your waypoint is now on the other side of shallower depths than you can travel.

As in, you have a route on the ICW that works fine, as long as you stay on the track. If you wander to one side or the other, your new track to that waypoint might now be impaired by varying depths that would not have been an issue on the original track. A friend ran aground because of this. Well, that and an issue of a 'new to him' boat and crossing into an area that didn't have the same chart coverage as he had been using in the 2 weeks prior. His flybridge chart plotter didn't have the same charts as the one below and he didn't realize this, and when he got off the track the plotter didn't have the data he needed to know about before using an XTE reset. It was a previously Florida-only boat, didn't have data for his now north of Beaufort location.

Now, none of that was equipment failure, all of it was captain error, but it's a mistake a great many people could likely make, especially with gear they're not familiar with using and in unknown waters.

Likewise, using the ICW as an example certainly opens up a whole other can of worms, as the conditions in some areas are known to vary from what the older data set in your plotter might contain (if it even has it at all). Further reasons to explain why depending on anything "automatic" stored in a plotter is NO guarantee of it's safety, and why most of them present those "not for actual use" kinds of warning messages.
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2005 Eastbay 47 FB - Solstice, w/Highfield CL360 tender
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Old 11-29-2022, 10:13 AM   #20
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City: Gooding ID/Wrangell AK
Vessel Name: Silver Bay
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TT,

Your post needs to be made a reference document. It’s what’s missing in every owners manual for autopilots and MFDs, the theory of operation or how it works.

The one question I have is can you take a route generated automatically and make it a regular route.

Tom
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