auto piliot vs chart plotter

[Watto]

From a navy navigators background, i wouldn't go anywhere without a chart, but thats just my state of mind.

Surely in this day and age, there is all in one units availale, combining chart plotter and auto?

on a side note, do the auto's run off a gryo or compass bearing, or by the heading recieved by gps?. if its gps feed that could be dangerous, as where ships head is is not usually where you are going

[mastreb]

Surely in this day and age, there is all in one units availale, combining chart plotter and auto?

on a side note, do the auto's run off a gryo or compass bearing, or by the heading recieved by gps?. if its gps feed that could be dangerous, as where ships head is is not usually where you are going

The Autopilot is actually just the actuator that turns the wheel and a controller that processes all the inputs to determine what to do. Autopilots typically include their own digital compass but none that I'm aware of use a real gyro. Without other instruments, all an autopilot can do is keep a heading.

The chartplotter, wind indicator, external compass, and GPS are all connected to the autopilot via a shipboard network, either NMEA 0183 for older systems or NMEA 2000 for newer (or by a vendor proprietary network, but that's rare these days). Because these networks are ubiquitous with instrument manufacturers, nobody makes a combined chartplotter/autopilot that I'm aware of. It's a simple thing to connect any chartplotter you want to any compatible autopilot.

[CampCook]

There are even NMEA 2000 to WiFi interfaces

I have a Lowrance sounder / chart plotter on the helm and plan to add a wheel pilot later this year. BUT, the above quote got my attention as I use the iPad for cruise planning prior to launch and in the cabin when anchored out. My problem is, I have not found a way to get my routes and waypoints from the iPad to the Lowrance. Normally this is done between a pc and a GPS using SD chips. Unfortunately, I have not found an SD writer for the iPad. It occurs to me that maybe this can be done via the NMEA 2000 interface. Any body know?

BTW, I have found the comments here very helpful.
Dave

[mastreb]

I have not found a way to get my routes and waypoints from the iPad to the Lowrance. Normally this is done between a pc and a GPS using SD chips. Unfortunately, I have not found an SD writer for the iPad. It occurs to me that maybe this can be done via the NMEA 2000 interface.

You will not be able to do this with an SD Card reader on the iPad. The devices that exist for this are solely for importing photos in the onboard photo app, and Apple has the file system locked down so that you can't just transfer arbitrary information that way.

The only interfaces you can transfer arbitrary information over are the network (WiFi or 3G), and so your only hope here is a NEMA to WiFi interface. It will get you the data-link, but then you'd have to find an iPad application that responds correctly to the NMEA sentences for Waypoint sync.

iNavX has an NMEA 0183 over TCP/IP client built into it so with Brookhouse iMux you could repeat NMEA 0183 from your chartplotter to WiFi. http://brookhouseonline.com/imux.htm

If you don't have an 0183 serial port coming off your chartplotter you'll need a NMEA2K to NMEA 0183 bridge as well: http://www.actisense.com/HTML/Products/ ... /index.php

I'm waiting for an iPad app that directly supports NMEA2000 PGNs. But most chartplotters have NMEA 0183 serial port outputs as well so it should be pretty simple to set this up.

Good luck!

[CampCook]

iNavX has an NMEA 0183 over TCP/IP client built into it so with Brookhouse iMux you could repeat NMEA 0183 from your chartplotter to WiFi.

WOW, that is way cool. The writeup at Brookhouse makes me salivate just thinking about the possibilities. It never occurred to me before to configure a complete integrated bridge on my little MacGregor. And, it is relatively inexpensive and easy to wire. Thanks for the help.
Dave with Gypsea Dream

[mastreb]

Dave--I won't be going this way with my boat but if you do implement the NMEA 0183 to WiFi interface you should definitely post a mod with your experience. I'd love to hear how it works.

[seahouse]

on a side note, do the auto's run off a gryo or compass bearing, or by the heading recieved by gps?. if its gps feed that could be dangerous, as where ships head is is not usually where you are going

A couple of summers ago I spent time on a boat with autohelm (Raymarine), but no chartplotter, and as I recall it used input from a fluxgate compass located midline on the hull to determine and maintain heading, as mastreb says.

[Québec 1]

on a side note, do the auto's run off a gryo or compass bearing, or by the heading recieved by gps?. if its gps feed that could be dangerous, as where ships head is is not usually where you are going

A couple of summers ago I spent time on a boat with autohelm (Raymarine), but no chartplotter, and as I recall it used input from a fluxgate compass located midline on the hull to determine and maintain heading, as mastreb says.

I was going to disconnect my fluxgate compas this year and run my s1 autopilot off my Garmin gpsmap 188c sounder compass. Are you saying this is dangerous?

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[CampCook]

Maestrb, If I get to do this install I will definitely post the results. Probably take a while to get it done. BTW, I found that the Navionics app also posts data via the wifi.
Dave on Gypsea Dream

[mastreb]

I was going to disconnect my fluxgate compas this year and run my s1 autopilot off my Garmin gpsmap 188c sounder compass. Are you saying this is dangerous?

I think it's perfectly safe: Modern chartplotters are constantly calibrating their digital compasses against GPS position-over-ground, so they are certainly more accurate than a fluxgate and probably more than a true gryo. No amount of precision flux determination or ded. reckoning beats actually knowing exactly where you are and extrapolating heading from that. I'm not sure why anyone would bother with an external compass sender if they've got a decent chartplotter--unless you're worried about the constellation of GPS satellites falling out of the sky, in which case you'll want a big old fashioned weams & plath compass and waterproof copies of all the NOAA charts.

I'm not sure exactly how accurate heading info for your specific chartplotter is, so as always nothing beats testing!

[Québec 1]

Great, that's what I thought! I'll let you guys know how it works.
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Anybody else on doing this?

[seahouse]

I think the term "dangerous" is used more figuratively in the sense that the difference between the direction the boat is heading and its course made good needs to be recognized.

The compass (with Autohelm) will simply maintain the boat on a set heading, which might not end up taking you to the destination point you wanted, if that's what you were expecting.
But the GPS, if programmed properly, will take you on a course to your destination point, regardless of the direction the boat is actually heading.

Best practise would suggest that you referr to the input from both sources. One supplements, but does not supplant, the other.

-B.

[CampCook]

I tried to reply to this before but suspect it was lost so will try again. WHY do you want to disconnect the flux gate? True, the satellites may not fall out of the sky but the chart plotter and GPS are certainly subject to failure leaving the "compass" as reasonable backup heading source. That is the kind of dissimilar redundancy systems engineers love. Also, the Raymarine pilot solution may very well use the internal gyro and compass as part of the GPS tracking solution. Typically, this is done to smooth or otherwise optimize performance. Of course, baring other failures, the disconnect should be safe but, why?

[Watto]

I think the term "dangerous" is used more figuratively in the sense that the difference between the direction the boat is heading and its course made good needs to be recognized.

The compass (with Autohelm) will simply maintain the boat on a set heading, which might not end up taking you to the destination point you wanted, if that's what you were expecting.
But the GPS, if programmed properly, will take you on a course to your destination point, regardless of the direction the boat is actually heading.

Best practise would suggest that you referr to the input from both sources. One supplements, but does not supplant, the other.

-B.

Thats exactly what I was getting at, your auto when tied in with your chart plotter should work out the compass heading you require to make your course made good (over ground) to your planned track. as long as the bearing that the auto read out tells you is your ships head bearing (the lubbers line) and not your course made good, all is sweet

[Québec 1]

I tried to reply to this before but suspect it was lost so will try again. WHY do you want to disconnect the flux gate? True, the satellites may not fall out of the sky but the chart plotter and GPS are certainly subject to failure leaving the "compass" as reasonable backup heading source. That is the kind of dissimilar redundancy systems engineers love. Also, the Raymarine pilot solution may very well use the internal gyro and compass as part of the GPS tracking solution. Typically, this is done to smooth or otherwise optimize performance. Of course, baring other failures, the disconnect should be safe but, why?

The AP manual says you have to disconnect the flux gate if you want the nmea to work as the AP will always start with the Flux Gate then go to seatalk then to nmea.
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