Hi we just bought a Columbia 34' and it came with a ST3000 auto pilot. we know nothing about these. Do they only work while motoring? If you buy the interface box and hook it up to a Garmin Chart plotter will it steer a plotted course? I just printed out the owners manual since it did not come with one. thanks for everyones help and I really like to ask all you other sailors here in the real world, instead of calling Raymaine and them telling me how it "should" work. thanks. Scott
Sailing w/ Autohelm ST3000
- Thread starter Amorita
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SeaTalk
I believe the ST designation stands for SeaTalk and means that is can communicate with other devices like a laptop. I upgraded to an ST3000 years ago on my Hunter 30 because the autopilot that came with it was an earlier Autohelm without the ST in the model number. I wired in connections to a handheld style of GPS and my laptop to use and a chartplotter. I could plot a course on the laptop, the gps would tell my laptop where we were and the laptop would tell the autopilot which way to steer. That was pretty cool but it all used way too much battery and my Hunter did not have much of a battery. Eventually I just used the autopilot to hold a course for me and used the laptop with Nobeltech software to plan my course. It does work while sailing, but you need to make certain that your batteries are up to the task. I now have a C350 with big batteries and a seperate starting battery. It has the ST4000 factory installed and works great sailing or motoring. It is even possible to add a wind vane that will allow that model to steer a course relative to the wind.
I believe the ST designation stands for SeaTalk and means that is can communicate with other devices like a laptop. I upgraded to an ST3000 years ago on my Hunter 30 because the autopilot that came with it was an earlier Autohelm without the ST in the model number. I wired in connections to a handheld style of GPS and my laptop to use and a chartplotter. I could plot a course on the laptop, the gps would tell my laptop where we were and the laptop would tell the autopilot which way to steer. That was pretty cool but it all used way too much battery and my Hunter did not have much of a battery. Eventually I just used the autopilot to hold a course for me and used the laptop with Nobeltech software to plan my course. It does work while sailing, but you need to make certain that your batteries are up to the task. I now have a C350 with big batteries and a seperate starting battery. It has the ST4000 factory installed and works great sailing or motoring. It is even possible to add a wind vane that will allow that model to steer a course relative to the wind.
ST3000
Were looking at adding a Garmin 492 chartplotter to the sailboat. I was just wondering how do the auto pilot know to look at the GPS for its course, its that was the NMEA interface box from raymarine does? or vise versa how does the GPS know to tell the auto pilot to work? We have 2 house batteries and a dedicated starting battery for the motor. Thanks for the Reply. Scott
Were looking at adding a Garmin 492 chartplotter to the sailboat. I was just wondering how do the auto pilot know to look at the GPS for its course, its that was the NMEA interface box from raymarine does? or vise versa how does the GPS know to tell the auto pilot to work? We have 2 house batteries and a dedicated starting battery for the motor. Thanks for the Reply. Scott
ST 3000
I think the ST3000 will not be quite big enough for that boat, at least not in any kind of rough weather. I have one temporarily on a 37, to take it home, and it works pretty good, when the weather co operates. Check the specks on it, and the weigt of your boat. I think you will find that you are right at the upper limits if not over them, for that auto pilot.
I think the ST3000 will not be quite big enough for that boat, at least not in any kind of rough weather. I have one temporarily on a 37, to take it home, and it works pretty good, when the weather co operates. Check the specks on it, and the weigt of your boat. I think you will find that you are right at the upper limits if not over them, for that auto pilot.
Course computer
On the system that I installed on my Hunter my lap top took care of that function and received input from the gps. It then output a signal to the autopilot. My C350 has a course computer than lives under the aft berth. That is probably the same type of device that you referred to as a MNEA interface box. The gps antenna, digital compass, knotmeter, auto pilot and radar all plug in to this computer which sorts it all out and makes the appropriate commands to the autopilot. It also sends data to the knotmeter so that it can display speed over ground or velocity made good (towards a waypoint) in addition to speed through the water.
On the system that I installed on my Hunter my lap top took care of that function and received input from the gps. It then output a signal to the autopilot. My C350 has a course computer than lives under the aft berth. That is probably the same type of device that you referred to as a MNEA interface box. The gps antenna, digital compass, knotmeter, auto pilot and radar all plug in to this computer which sorts it all out and makes the appropriate commands to the autopilot. It also sends data to the knotmeter so that it can display speed over ground or velocity made good (towards a waypoint) in addition to speed through the water.
ST3000
Hi, My boat (28' Newport) came with an Autohelm 3000. I think it's same basic pilot. Mine works great in all conditions except for large (4') following seas. Then I do a better job of steering, otherwise the AP is better than I am. Anyway, it works under sail and under motor, as long as boat is moving forward it will steer. I guess you could connect it to a GPS so it would follow a course, but why bother? When I am trying to go somewhere (instead of just sailing around), I set the course on my GPS, turn on the autopilot, and then aim the boat at the waypoint. With the GPS I can tell if I'm off course or not and it's easy enough to make course corrections of 1 degree if necessary. When I reach the waypoint, I change heading to the next one, and so on. With a sail boat, sails need to be trimmed, etc. so that I would not want the autopilot to make a larger course change without me knowing. Good luck, Barry
Hi, My boat (28' Newport) came with an Autohelm 3000. I think it's same basic pilot. Mine works great in all conditions except for large (4') following seas. Then I do a better job of steering, otherwise the AP is better than I am. Anyway, it works under sail and under motor, as long as boat is moving forward it will steer. I guess you could connect it to a GPS so it would follow a course, but why bother? When I am trying to go somewhere (instead of just sailing around), I set the course on my GPS, turn on the autopilot, and then aim the boat at the waypoint. With the GPS I can tell if I'm off course or not and it's easy enough to make course corrections of 1 degree if necessary. When I reach the waypoint, I change heading to the next one, and so on. With a sail boat, sails need to be trimmed, etc. so that I would not want the autopilot to make a larger course change without me knowing. Good luck, Barry
ST3000
Thanks for all the replys. Barry so your saying you get sailing towards your way point, once your sails are all trimmed. you just turn the AP on, or are you having to put a certain degree into it so it knows where to do, does the AP correct for current and wind on the side of the boat, to keep you on course. We are not wanting the boat to sail its self but would like it to sail on AP so we don't have to sit there and hold the wheel for hours at a time on our way to our destination. Thanks Scott
Thanks for all the replys. Barry so your saying you get sailing towards your way point, once your sails are all trimmed. you just turn the AP on, or are you having to put a certain degree into it so it knows where to do, does the AP correct for current and wind on the side of the boat, to keep you on course. We are not wanting the boat to sail its self but would like it to sail on AP so we don't have to sit there and hold the wheel for hours at a time on our way to our destination. Thanks Scott
The autopilot is getting data from the fluxgate
compass so when you turn it on it is set to steer the heading displayed. The AP will try to maintain this heading only (or whatever heading you set it to). A GPS set to a waypoint will account for any leeway due to currents etc. which is affecting your course. While my GPS is linked to the AP I prefer to operate as Barry suggested by matching the AP's course to the GPS track. It's easier to adjust your heading using the AP to take advantage of wind shifts which help (a lift) or avoid being "headed" by disadvantageous shifts. When GPS and AP are linked you "tell" the AP you want it in "track" mode which means it will take it's data from the GPS.
compass so when you turn it on it is set to steer the heading displayed. The AP will try to maintain this heading only (or whatever heading you set it to). A GPS set to a waypoint will account for any leeway due to currents etc. which is affecting your course. While my GPS is linked to the AP I prefer to operate as Barry suggested by matching the AP's course to the GPS track. It's easier to adjust your heading using the AP to take advantage of wind shifts which help (a lift) or avoid being "headed" by disadvantageous shifts. When GPS and AP are linked you "tell" the AP you want it in "track" mode which means it will take it's data from the GPS.
AP Use
Hello, On my boat when I am navigating a course, I have the route set in my GPS. My GPS will display my current track (direction the boat if moving) and the desired course (the direction to the waypoint). To use the autopilot, I put the boat on the proper course, then press the 'auto' button on the AP. The AP will then keep the boat on the course. If the current changes and the boat starts moving off course, I can press the +1 or -1 button to get the boat back on course. It's easier to do it than to describe it. One last thing, the AP also has an auto tack feature. Press the +10 and +1 button at the same time and the boat will turn 100 degrees to starboard. Pressing the two - buttons tacks to port. Very handy if you single hand. Barry
Hello, On my boat when I am navigating a course, I have the route set in my GPS. My GPS will display my current track (direction the boat if moving) and the desired course (the direction to the waypoint). To use the autopilot, I put the boat on the proper course, then press the 'auto' button on the AP. The AP will then keep the boat on the course. If the current changes and the boat starts moving off course, I can press the +1 or -1 button to get the boat back on course. It's easier to do it than to describe it. One last thing, the AP also has an auto tack feature. Press the +10 and +1 button at the same time and the boat will turn 100 degrees to starboard. Pressing the two - buttons tacks to port. Very handy if you single hand. Barry
I'm with Barry on use of GPS and AP
Mine are not connected, so the GPS does not direct the AP. I get my course from the GPS charplotter, point the boat on that heading, engage the AP and press"auto" funtion. As Barry said you may frequently have to make heading changes on the AP beause of leeway and tidal current. One advantage of being able to steer independant of the GPS, is you can do some estimating as to most efficient course. Say your next way point/home marina is across the bay at a bearing of 90 (east) five nm distance. Wind is out of the north and the tidal current is setting to the south at .5 knt. LEt say boat speed is 5 knt so it will take me an hour to cross the bay. I gustimate that I am making .25 knt leeway to the south. So during an hour hour I will be set south .75 nm. So I get a bearing off the ploter to a point .75 nm north of the marina ( says its 80 degrees) put the boat on an 80 degree heading and click on the AP. If my calculations were perfect, the compass would show boat pointed at 80, but the GPS would show the boat was moving along at 90 degrees, "crabbing" across the bay. If I had the GPS/AP drive the boat, it would start of at 90, then while crossing the bay, it would adjust to 80, then to 70 then to 60 ( made up numbers) but it would drive the boat in an arch across the bay. Did I get that right Barry?
Mine are not connected, so the GPS does not direct the AP. I get my course from the GPS charplotter, point the boat on that heading, engage the AP and press"auto" funtion. As Barry said you may frequently have to make heading changes on the AP beause of leeway and tidal current. One advantage of being able to steer independant of the GPS, is you can do some estimating as to most efficient course. Say your next way point/home marina is across the bay at a bearing of 90 (east) five nm distance. Wind is out of the north and the tidal current is setting to the south at .5 knt. LEt say boat speed is 5 knt so it will take me an hour to cross the bay. I gustimate that I am making .25 knt leeway to the south. So during an hour hour I will be set south .75 nm. So I get a bearing off the ploter to a point .75 nm north of the marina ( says its 80 degrees) put the boat on an 80 degree heading and click on the AP. If my calculations were perfect, the compass would show boat pointed at 80, but the GPS would show the boat was moving along at 90 degrees, "crabbing" across the bay. If I had the GPS/AP drive the boat, it would start of at 90, then while crossing the bay, it would adjust to 80, then to 70 then to 60 ( made up numbers) but it would drive the boat in an arch across the bay. Did I get that right Barry?
Plus, depending on wind direction ...
You could end up on a bearing that you eventually can't make.
You could end up on a bearing that you eventually can't make.
Track mode
I have a Autohelm 3000 on my Hunter 35.5. While it is underpowered for the boat it will do not bad job under light to moderate winds or while motoring. It is tied into the seatalk bus which includes GPS and will track a directly to a waypoint if required and when selected to TRACK mode. When in track mode the autopilot will track DIRECT to the selected waypoint and will provide automatic drift correction while in that mode - it will not do an arc as you suggest. I only use this mode if I am motoring because the continuous course corrections made by the autopilot in track mode to maintain the desired course make for constant sail trimming. When sailing I use the autopilot on heading or wind vane mode and use GPS only to determine my X-track off the rhumb line to my selected waypoint. Vane mode will maintain a constant wind angle and works especially well on a close reach or DDW.
I have a Autohelm 3000 on my Hunter 35.5. While it is underpowered for the boat it will do not bad job under light to moderate winds or while motoring. It is tied into the seatalk bus which includes GPS and will track a directly to a waypoint if required and when selected to TRACK mode. When in track mode the autopilot will track DIRECT to the selected waypoint and will provide automatic drift correction while in that mode - it will not do an arc as you suggest. I only use this mode if I am motoring because the continuous course corrections made by the autopilot in track mode to maintain the desired course make for constant sail trimming. When sailing I use the autopilot on heading or wind vane mode and use GPS only to determine my X-track off the rhumb line to my selected waypoint. Vane mode will maintain a constant wind angle and works especially well on a close reach or DDW.
Ummm ... no ...
It depends on the software. Most AP's (like the ST Autohelms) do not steer the boat on a constant heading when in track mode. They steer to minimize XTE (Cross Track Error). Thus they automatically compensate for wind and current. In the situation that Scott describes, he is doing classic piloting and adjusting course to eliminate cross track error, just as the AP would if it was following a GPS track. The two NMEA sentances for autopilots are APA and APB. APA - Autopilot Sentence "A" 1 2 3 4 5 6 7 8 9 10 11 | | | | | | | | | | | $--APA,A,A,x.xx,L,N,A,A,xxx,M,c---c*hh<CR><LF> Field Number: 1) Status V = LORAN-C Blink or SNR warning V = general warning flag or other navigation systems when a reliable fix is not available 2) Status V = Loran-C Cycle Lock warning flag A = OK or not used 3) Cross Track Error Magnitude 4) Direction to steer, L or R 5) Cross Track Units (Nautic miles or kilometers) 6) Status A = Arrival Circle Entered 7) Status A = Perpendicular passed at waypoint 8) Bearing origin to destination 9) M = Magnetic, T = True 10) Destination Waypoint ID 11) checksum APB - Autopilot Sentence "B" 13 15 1 2 3 4 5 6 7 8 9 10 11 12| 14| | | | | | | | | | | | | | | | $--APB,A,A,x.x,a,N,A,A,x.x,a,c--c,x.x,a,x.x,a*hh<CR><LF> Field Number: 1) Status V = LORAN-C Blink or SNR warning V = general warning flag or other navigation systems when a reliable fix is not available 2) Status V = Loran-C Cycle Lock warning flag A = OK or not used 3) Cross Track Error Magnitude 4) Direction to steer, L or R 5) Cross Track Units, N = Nautical Miles 6) Status A = Arrival Circle Entered 7) Status A = Perpendicular passed at waypoint 8) Bearing origin to destination 9) M = Magnetic, T = True 10) Destination Waypoint ID 11) Bearing, present position to Destination 12) M = Magnetic, T = True 13) Heading to steer to destination waypoint 14) M = Magnetic, T = True 15) Checksum Most of the information is the same. APB adds "Bearing, present position to Destination" and "Heading to steer to destination waypoint" Navigation software that outputs the APB sentence and autopilots that can use the extra information will sail a smoother course than AP's that use APA. In either case the AP/GPS combo is very unlikely yo steer and arc like a human helmsman would.
It depends on the software. Most AP's (like the ST Autohelms) do not steer the boat on a constant heading when in track mode. They steer to minimize XTE (Cross Track Error). Thus they automatically compensate for wind and current. In the situation that Scott describes, he is doing classic piloting and adjusting course to eliminate cross track error, just as the AP would if it was following a GPS track. The two NMEA sentances for autopilots are APA and APB. APA - Autopilot Sentence "A" 1 2 3 4 5 6 7 8 9 10 11 | | | | | | | | | | | $--APA,A,A,x.xx,L,N,A,A,xxx,M,c---c*hh<CR><LF> Field Number: 1) Status V = LORAN-C Blink or SNR warning V = general warning flag or other navigation systems when a reliable fix is not available 2) Status V = Loran-C Cycle Lock warning flag A = OK or not used 3) Cross Track Error Magnitude 4) Direction to steer, L or R 5) Cross Track Units (Nautic miles or kilometers) 6) Status A = Arrival Circle Entered 7) Status A = Perpendicular passed at waypoint 8) Bearing origin to destination 9) M = Magnetic, T = True 10) Destination Waypoint ID 11) checksum APB - Autopilot Sentence "B" 13 15 1 2 3 4 5 6 7 8 9 10 11 12| 14| | | | | | | | | | | | | | | | $--APB,A,A,x.x,a,N,A,A,x.x,a,c--c,x.x,a,x.x,a*hh<CR><LF> Field Number: 1) Status V = LORAN-C Blink or SNR warning V = general warning flag or other navigation systems when a reliable fix is not available 2) Status V = Loran-C Cycle Lock warning flag A = OK or not used 3) Cross Track Error Magnitude 4) Direction to steer, L or R 5) Cross Track Units, N = Nautical Miles 6) Status A = Arrival Circle Entered 7) Status A = Perpendicular passed at waypoint 8) Bearing origin to destination 9) M = Magnetic, T = True 10) Destination Waypoint ID 11) Bearing, present position to Destination 12) M = Magnetic, T = True 13) Heading to steer to destination waypoint 14) M = Magnetic, T = True 15) Checksum Most of the information is the same. APB adds "Bearing, present position to Destination" and "Heading to steer to destination waypoint" Navigation software that outputs the APB sentence and autopilots that can use the extra information will sail a smoother course than AP's that use APA. In either case the AP/GPS combo is very unlikely yo steer and arc like a human helmsman would.
Now Were Getting Technical
Wow thanks again for all the replys. I guess my main question was is it worth it to spend the $150 for the seatalk interface box to hook our gps and our auto pilot together. Or are we just better of setting a gps course getting on track and turing the auto pilot on and make small adjustments as needed? Scott
Wow thanks again for all the replys. I guess my main question was is it worth it to spend the $150 for the seatalk interface box to hook our gps and our auto pilot together. Or are we just better of setting a gps course getting on track and turing the auto pilot on and make small adjustments as needed? Scott
I agree with the latter
I find that keeping your head outside the boat is greatly encouraged by avoiding interfacing things together. That's probably because I haven't and is only one man's opinion.
I find that keeping your head outside the boat is greatly encouraged by avoiding interfacing things together. That's probably because I haven't and is only one man's opinion.
Hi Scott, I have the GPS feeding course ...
data to the autopilot on our boat while motoring. I prefer it this way than before the two were connected. It makes all the necessary course corrections enroute and will reach the next waypoint dead on. These corrections I had to make manually before the connection. It makes cruising much more pleasant, albeit less involved. It is less often that I use the AP while under sail mainly because the wind direction and desired course conflict. Either way we miraculously end up at the same point. Trust the electromechanical method to get you to your destination, not to worry how accurate the beeline, unless you're racing, IMHO. Terry
data to the autopilot on our boat while motoring. I prefer it this way than before the two were connected. It makes all the necessary course corrections enroute and will reach the next waypoint dead on. These corrections I had to make manually before the connection. It makes cruising much more pleasant, albeit less involved. It is less often that I use the AP while under sail mainly because the wind direction and desired course conflict. Either way we miraculously end up at the same point. Trust the electromechanical method to get you to your destination, not to worry how accurate the beeline, unless you're racing, IMHO. Terry
Moody, I am confused
I thought the GPS/AP could only get you to a waypoint, that the system can't run the boat on a straight line when the boat is slipping sideways due to leeway/current/ wind waves. In my example above ( fake numbers) I want to end up at a waypoint 5 nm due east (90 degrees) while being set to the south. If my calculations are correct, I point the bow at 80 degrees and get underway and the GPS will show the boat is actually moving along 90 degrees. So my track sailed will be a straight line. Is this correct? I don't understand how the GPS driving the boat can maintain a track. Isn't the GPS just heading to a mark and doesn't care how it gets there? Or will the GPS/AP try to get the boat onto the 90 degree line by seting up an 80 degree heading? Or use this example: I want to go along the shore for 5 miles to a waypoint .5 nm off the beach. There is an on- shore wind and I am heading up wind, so I have lee way and lee shore. If I puch in "steer to" to the waypoint 5 nm upwind and .5 nm off the the beach, is there a chance I will end up on the beach?
I thought the GPS/AP could only get you to a waypoint, that the system can't run the boat on a straight line when the boat is slipping sideways due to leeway/current/ wind waves. In my example above ( fake numbers) I want to end up at a waypoint 5 nm due east (90 degrees) while being set to the south. If my calculations are correct, I point the bow at 80 degrees and get underway and the GPS will show the boat is actually moving along 90 degrees. So my track sailed will be a straight line. Is this correct? I don't understand how the GPS driving the boat can maintain a track. Isn't the GPS just heading to a mark and doesn't care how it gets there? Or will the GPS/AP try to get the boat onto the 90 degree line by seting up an 80 degree heading? Or use this example: I want to go along the shore for 5 miles to a waypoint .5 nm off the beach. There is an on- shore wind and I am heading up wind, so I have lee way and lee shore. If I puch in "steer to" to the waypoint 5 nm upwind and .5 nm off the the beach, is there a chance I will end up on the beach?
Try this thought process:
Forget about the complications of leeway and drift when sailing, and as an example for better understanding, ONLY consider how the autopilot works if you are going from A to B with a current that is perpendicular to the line between A and B (like, say, when you are motoring!). This is without a GPS connection to the AP. Our experience has been that you need to look at the XTE (cross track error) as you are moving along. Say you leave point A and set the AP for a heading to point B, straight line. This is without a GPS. As the current pushes the boat away from the direct (rhumb) line between the two points, the autopilot will keep that heading, the course you put in (also forget about boat heading being different than COG) and will NOT compensate for the current. The XTE will start to grow. Your final motored course will be to one side of the rhumb line because the autopilot didn't know about the current. The AP has NO WAY to compensate for current. You will eventually get to a spot away from point B because the AP, by itself, didn't know you wanted to go to a point, but just kept the boat on the heading you put into the AP. The AP doesn't know where you want to go, it only knows a heading to continue to steer. ONLY with a GPS interface will the AP be controlled to continue to change its input heading go to point B with the current setting you off. Alternatively, you could have figured out the drift before you left point A and told the autopilot to steer further left (or right) of point B before you left point A, in which case you should, theoretically, have been able to motor along the rhumb line, without a GPS. It's really no different than hand steering, regardless of whether you are figuring drift, current, leeway or whatever knocks your boat off a rhumb line course from any point to another point.
Forget about the complications of leeway and drift when sailing, and as an example for better understanding, ONLY consider how the autopilot works if you are going from A to B with a current that is perpendicular to the line between A and B (like, say, when you are motoring!). This is without a GPS connection to the AP. Our experience has been that you need to look at the XTE (cross track error) as you are moving along. Say you leave point A and set the AP for a heading to point B, straight line. This is without a GPS. As the current pushes the boat away from the direct (rhumb) line between the two points, the autopilot will keep that heading, the course you put in (also forget about boat heading being different than COG) and will NOT compensate for the current. The XTE will start to grow. Your final motored course will be to one side of the rhumb line because the autopilot didn't know about the current. The AP has NO WAY to compensate for current. You will eventually get to a spot away from point B because the AP, by itself, didn't know you wanted to go to a point, but just kept the boat on the heading you put into the AP. The AP doesn't know where you want to go, it only knows a heading to continue to steer. ONLY with a GPS interface will the AP be controlled to continue to change its input heading go to point B with the current setting you off. Alternatively, you could have figured out the drift before you left point A and told the autopilot to steer further left (or right) of point B before you left point A, in which case you should, theoretically, have been able to motor along the rhumb line, without a GPS. It's really no different than hand steering, regardless of whether you are figuring drift, current, leeway or whatever knocks your boat off a rhumb line course from any point to another point.
really very simple
Hi, With a GPS it's really very simple to use the AP to get you to a waypoint WITHOUT the AP and GPS units being connected. The key is to make sure the boat is following the proper course provided by the GPS. You may need to make course corrections to stay on track. As long as you make the required changes, you will make it to the waypoint. Pick a waypoint and have the GPS navigate to it. The GPS will show you the course you need to head to make it to the waypoint. Put the boat on that heading, and you WILL make it to the waypoint. You don't need to worry about drift, leeway, currents, or anything else. The GPS doesn't know about any of those things, nor does it need to. All the GPS knows is that you need to head 'this way' (heading AAA degrees) to get there. As long as you steer the boat so that it is on the proper heading you will make it (and the GPS will give you the ETA too). Please note that the direction the boat is headed may not be the direction the boat is pointed. If you use a simple example of a waypoint 10 miles due north of your current location, and a current moving due east, the boat may be pointed at 350 degrees, but moving due north. With a GPS providing a course for you, you must make sure the boat is following the course. Your magnetic compass may not be useful in this situation, so follow the GPS. As currents, wind, etc. change, the GPS course will automatically change to point the way to the waypoint. If your AP and GPS are not connected, you may have to make course corrections to stay on track. As long as you check every few minutes you will get there, and with very little cross track error. Barry
Hi, With a GPS it's really very simple to use the AP to get you to a waypoint WITHOUT the AP and GPS units being connected. The key is to make sure the boat is following the proper course provided by the GPS. You may need to make course corrections to stay on track. As long as you make the required changes, you will make it to the waypoint. Pick a waypoint and have the GPS navigate to it. The GPS will show you the course you need to head to make it to the waypoint. Put the boat on that heading, and you WILL make it to the waypoint. You don't need to worry about drift, leeway, currents, or anything else. The GPS doesn't know about any of those things, nor does it need to. All the GPS knows is that you need to head 'this way' (heading AAA degrees) to get there. As long as you steer the boat so that it is on the proper heading you will make it (and the GPS will give you the ETA too). Please note that the direction the boat is headed may not be the direction the boat is pointed. If you use a simple example of a waypoint 10 miles due north of your current location, and a current moving due east, the boat may be pointed at 350 degrees, but moving due north. With a GPS providing a course for you, you must make sure the boat is following the course. Your magnetic compass may not be useful in this situation, so follow the GPS. As currents, wind, etc. change, the GPS course will automatically change to point the way to the waypoint. If your AP and GPS are not connected, you may have to make course corrections to stay on track. As long as you check every few minutes you will get there, and with very little cross track error. Barry
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