Compass, what stinking compass.

[caltexflanc]

The Simrad is not connected to a heading sensor, nor auto pilot. The picture of the garmin at that present time the AP was not hooked up to it, but it now is. So I'll have to check and see if it's right. That's one of the additions we have to do the network is add a heading sensor. Ultimately we want a full maretron monitoring package but were going wait a while. Also a N2K weather station is next on the list.

I did say "likely" Then the Simrad last sensed/registered the boat going forward. it may be more or less sensitive than the Garmin as to when it denotes a change. Do you have a radar with MARPA/ARPA and/or overlay?

 

[N4712]

I did say "likely" Then the Simrad last sensed/registered the boat going forward. it may be more or less sensitive than the Garmin as to when it denotes a change. Do you have a radar with MARPA/ARPA and/or overlay?

Yes we have the Simrad broadband hooked into the Simrad which has MARPA. This is the only pic I have right now, but I'll get one later. I have played with it at the dock and it's excellent in close range I could see as close as 300 ft, in makes out my slip nod the whole marina canal, and the main canal. Great Technology! But for farther range seeing (it's not good at that) I have a simrad stand alone, which also works like a charm.(second pic)

 

[caltexflanc]

If you have Marpa, then there is a heading sensor in there somewhere; on some Simrads it is built into the radar dome I believe.

Edit: looked at Simrad broad band manual, looks like they still call for an external RC42 compass (heading sensor) for Marpa.

 

[Scary]

Wow

A lot of interesting comments. I personally use the compass only as back up. I navigate with a 12kw high def radar with chart overlay. Backed up with Rose Point on a laptop as well as a backup chartplotter and hand held gps. Course heading is usually maintained by Auto, the best helmsman on the boat. The problem with using a compass for navigation is cross track error. There are so many variables effecting course. Waves wind and current radically effect course over the ground. If you navigate with any of these factors all the compass can do is tell you where your pointed. If you navigate in currents like those in Ak or Bc they can and do move in erratic directions and often with great velocity. Compass heading approaching the Golden Gate from the Farralon Islands will be as much 35 deg north of cog because of wind and wave action plus a 1/2 knt current moving south. The slower the boat the more the elements effect cross track error. A friend of mine is a old time airplane pilot he relies heavily on his compass. we've had this discussion many times, if your flying at 120 knts, 6 knts of cross wind is not a big factor compared to 6knt of cross current on a 6knt boat. If your in really rough conditions and your boat is swinging thru 30plus deg a compass is hard to follow let alone no what your real course over the ground is. I guess if your good enough to know and plot all of these factors you could navigate with compass and a paper chart. Personally I love these new electronic gismos especially the high def radar overlay on my chart plotter.

 

[N4712]

If you have Marpa, then there is a heading sensor in there somewhere; on some Simrads it is built into the radar dome I believe. Edit: looked at Simrad broad band manual, looks like they still call for an external RC42 compass (heading sensor) for Marpa.

Hmm, weird. We Only have 2 heading sensors for AP and back up AP. I'll have to dig, and see but I'm pretty sure. Maybe it's connected into the AP sensor? But I know I can't send data to the ap, because I have tried before.

 

[caltexflanc]

On a networked system, yeah, (which could be as basic as NMEA 0183 if wired right) it could be, I am not all that familiar with newer Simrad but on Furuno for instance one compass can feed the whole system. I had two because the Furuno radar required a proprietary AD10 output for some functions in addition to NMEA, which the Roberston AP's compass did not have, which ended up being a spare.

 

[psneeld]

A lot of interesting comments. I personally use the compass only as back up. I navigate with a 12kw high def radar with chart overlay. Backed up with Rose Point on a laptop as well as a backup chartplotter and hand held gps. Course heading is usually maintained by Auto, the best helmsman on the boat. The problem with using a compass for navigation is cross track error. There are so many variables effecting course. Waves wind and current radically effect course over the ground. If you navigate with any of these factors all the compass can do is tell you where your pointed. If you navigate in currents like those in Ak or Bc they can and do move in erratic directions and often with great velocity. Compass heading approaching the Golden Gate from the Farralon Islands will be as much 35 deg north of cog because of wind and wave action plus a 1/2 knt current moving south. The slower the boat the more the elements effect cross track error. A friend of mine is a old time airplane pilot he relies heavily on his compass. we've had this discussion many times, if your flying at 120 knts, 6 knts of cross wind is not a big factor compared to 6knt of cross current on a 6knt boat. If your in really rough conditions and your boat is swinging thru 30plus deg a compass is hard to follow let alone no what your real course over the ground is. I guess if your good enough to know and plot all of these factors you could navigate with compass and a paper chart. Personally I love these new electronic gismos especially the high def radar overlay on my chart plotter.

Pretty well sums it up...the old ways need certain "mindsets"...GPS nav with a radar is about as exact as you can get it with a backup even...the compass is there for the once in a million total nav loss...after 14 years of commercial captaining...GPS has never burped enough for me to ever worry about...now in certain parts of the globe I would be more cautions due to limited WAAS and it brethren.

 

[janice142]

I use the compass almost exclusively. I will confirm heading via OpenCPN but once I'm on track I write down my compass heading and continue. It's easier for me.

That said, often I listen to the Loopers as they head across the Gulf. I hear way-points and estimated arrivals (down to the minute) at such-and-such knots. I might hear "turning east to Marker 26" but not the compass heading. It's more like star-ship navigation rather than cruising. Exciting, but different too.

As for the GPS, it's only on when I get close to anchoring. I want a trail so IF I had to leave at oh-dark-thirty I'd have some bread crumbs to follow out. That's a handy feature. I'm sure there are more features on my Garmin76 that I've not mastered and one of these days I might learn 'em.

 

[markpierce]

Scary, I've experienced the same. So far, thankfully, I've returned home.

 

[Wxx3]

Till I put radar on the trawler...or still on my assistance towing vessel, I use a compass for turning at night or low vis. GPS often responds slowly enough in very tight quarters you can overshoot real easy in a sharp turn. A compass doesn't have to be accurate to use it in this mode...it's really just for turning the appropriate number of degrees to the new course.

I do adjust them with the GPS now...very easy...yes I've heard all the old timer arguments why it doesn't work...but I'm using "modern thinking" so it works just fine....

For all it's "oldness" it works and actually as the boat is pitching up and down and rolling side to side, it is far more accurate than my F..I mean Fluxgate compass.

Just today, my autopilot went south, while the rest of us where going north ( I kept on wondering why the boat kept on turning). One quarter second glance at my compass told me the problem.

and as PS said, COG is delayed, not my much, but still delayed. In bad visibility, I will use the mag compass to steer a heading and then correct occasionally looking at COG. If you just steer by COG you will look like a drunk rooster being chased my 3 foxes, in a hen house of turkeys.


I may not use it, but I would never do without it.

 

[N4712]

Here are pics I just took, also note the erratic tracks that happen when moored.

 

[caltexflanc]

A lot of interesting comments. I personally use the compass only as back up. I navigate with a 12kw high def radar with chart overlay. Backed up with Rose Point on a laptop as well as a backup chartplotter and hand held gps. Course heading is usually maintained by Auto, the best helmsman on the boat. The problem with using a compass for navigation is cross track error. There are so many variables effecting course. Waves wind and current radically effect course over the ground. If you navigate with any of these factors all the compass can do is tell you where your pointed. If you navigate in currents like those in Ak or Bc they can and do move in erratic directions and often with great velocity. Compass heading approaching the Golden Gate from the Farralon Islands will be as much 35 deg north of cog because of wind and wave action plus a 1/2 knt current moving south. The slower the boat the more the elements effect cross track error. A friend of mine is a old time airplane pilot he relies heavily on his compass. we've had this discussion many times, if your flying at 120 knts, 6 knts of cross wind is not a big factor compared to 6knt of cross current on a 6knt boat. If your in really rough conditions and your boat is swinging thru 30plus deg a compass is hard to follow let alone no what your real course over the ground is. I guess if your good enough to know and plot all of these factors you could navigate with compass and a paper chart. Personally I love these new electronic gismos especially the high def radar overlay on my chart plotter.

I learned to navigate with paper charts and plotting equipment such as parallel rules, compasses/dividers etc. calculating current vectors was part of it. Took the course in and specifically for SFO. US Sailing . Even if you choose to go all electronic, which I have no particular argument with beyond the experience of things on a boat inevitably stopping to function and at the worst time, it is very useful, I would even say beautiful, to understand exactly what the water and wind are doing and how it affects your boat. Puts you more at one with your environment. Plus I am one of those types that enjoyed the sport of man against machine, my plots and ETA's vs plotter. Don't get me wrong, I loves me gizmos. if it weren't for selling a bunch of electronic gizmos, I'd never been able to go boating!