Position of Heading Sensor?

[Dockhead]

Classically, it was always the rule that the heading sensor needed to right at the roll and pitch center of the boat for best performance.

I wonder if that is really still the case now that we have heading sensors with excellent accelerometer correction of the heading data?

Airmar are apparently discontinuing (!) their H2183 gyrocompass, which was supposed to be the best device of this type by far that you could buy for less than many thousands of dollars. It has three axis accelerometers and a three axis gyro and will apparently give 2 degrees of heading accuracy in dynamic conditions -- incomparably better than the old fluxgate, and much better than similar devices by Maretron (OEM to Raymarine, Furuno, etc.). See: Panbo: The Marine Electronics Weblog: Airmar H2183 compass, best in class?.
Airmar say that the combined GPS and heading sensor, meant to be rail mounted, is the replacement.

What do you guys think? Should I chase one of the apparently discontinued H2183 in order to put it where it's supposed to be? Or give in to "progress" and be happy to have the newfangled thing on my rail? I'm very picky about heading data -- it's what makes MARPA and radar overlay work properly, and it's what makes your pilot steer well. It's really important.

[goboatingnow]

Autonic do a range of corrected heading devices.

Dockhead, if you reaally are interested in good heading data, why not go teh whole hog and buy a satellite compass. I have an OEM version of the hemisphere GPS 'vector' unit and boy you should see the stabilty of the Marpa unit when its connected.

get one of these and put it in a box Precision - OEM Components/Antennas - Hemisphere GPS

[Dockhead]

Originally Posted by goboatingnow

Autonic do a range of corrected heading devices.

Dockhead, if you reaally are interested in good heading data, why not go teh whole hog and buy a satellite compass. I have an OEM version of the hemisphere GPS 'vector' unit and boy you should see the stabilty of the Marpa unit when its connected.

get one of these and put it in a box Precision - OEM Components/Antennas - Hemisphere GPS

Hmm, that's a thought!! So you're actually using one of those??! Can you share your setup? Where can you buy that and how much does it cost?

I notice that even the Furuno satellite compass has come down in price -- now about $2000.

Really, maybe that's just the thing!

[Dockhead]

I just Googled these -- they are sick!! Position accuracy in the millimeters, and heading accuracy in the hundredths of a degree!!

Can't find any information about cost, however, afraid I am just being teased . . . where can you buy them?

[goboatingnow]

Mine was an OEM project for a customer that never went ahead with the project, so I mounted the board in a 20 euros aluminium box, and connected two standard Garmin GA29 antennas, mounted 0.8m apart on a horizontal pole. Most nowdays are all built into the antenna housing. ( like SImrad, furuno and Henisphere Vector)

The unit has an integrated fluxgate and rate gryo stabilised sensor which supplements the GPS unit , if the GPS signal disappears.

Ive found it very good, much better then any fluxgate compass, no matter how stabilised
1-5-10Hz heading updates. My one is 0183, but the later ones are N2K ( I built a n2k controller for it) . It feeds into the chartplotter like any other heading input. Theres no setup needed ( in general) it just works. see Real Time Kinematic - Wikipedia, the free encyclopedia

PS, I get very high accuracy positioning as well. But the compass system doesn't use the actual GPS position, it use the phase relationship between the two antennas, It works even when the boat is static. ( its bizzare to see it work as I turn the antennas in the office.

They are often ignored on leisure boats, but have come seriously down in cost and in my opinion will soon overtake high end fluxgate.

Dave

[goboatingnow]

Originally Posted by Dockhead

I just Googled these -- they are sick!! Position accuracy in the millimeters, and heading accuracy in the hundredths of a degree!!

Can't find any information about cost, however, afraid I am just being teased . . . where can you buy them?

The dealer for hemispheregps is ( was) in the isle of Man.

mine originally came direct from canada at 700 CDN !!. email hemisphere they were ( are) a nice company to deal with . They IPOed so who knows now! if I remember they supplied me from a subsidiary in Arizona

Dave

[Dockhead]

So, you've got one you built up with an N2K controller? I reckon NMEA 0183 would be ok too -- just feed it to one of the MFD's or to the course computer and it will bridge onto the N2K net.

So, you got stuck with a project the client didn't take? Wanna sell it?

[goboatingnow]

Originally Posted by Dockhead

So, you've got one you built up with an N2K controller? I reckon NMEA 0183 would be ok too -- just feed it to one of the MFD's or to the course computer and it will bridge onto the N2K net.

So, you got stuck with a project the client didn't take? Wanna sell it?

well no , right now I couldnt sell it as it not really in a proper case and requires a awkward setup routine, works well though.. ( also i have an idea for another project!).

The Vector OEM board at the time only did 0183, but the client wanted n2k in the design and we have a n2K stack.

If you are spending the bucks your are spending I really would consider the option. its far better then a flux based heading sensor. Very common now on steel trawlers ( for obvious reasons). Its actually better then a proper Gyro. IMHO.

PS I was paid quite handsomely for the development time. The board was effectively a freebie.
Dave

[Dockhead]

Originally Posted by goboatingnow

well no , right now I couldnt sell it as it not really in a proper case and requires a awkward setup routine, works well though.. ( also i have an idea for another project!).

The Vector OEM board at the time only did 0183, but the client wanted n2k in the design and we have a n2K stack.

If you are spending the bucks your are spending I really would consider the option. its far better then a flux based heading sensor. Very common now on steel trawlers ( for obvious reasons). Its actually better then a proper Gyro. IMHO.

PS I was paid quite handsomely for the development time. The board was effectively a freebie.
Dave

OK, I understand. Hemisphere sells a ready made system -- I'll try to get in touch and find out how much they sell it for. And I guess in the worst case I could just go with the Furuno system, which is fully developed, ready made, documented, etc., and only costs a couple grand. Great idea, anyway, thanks for it!

[goboatingnow]

HemisphereGps make two off the shelf units ( fully ready to go and documented)



They used to be cheaper then Furuno/Simrad, but maybe the prices have narrowed.

dave

[Dockhead]

Cheaper? But they are much more accurate, aren't they? That looks like the way to go!

[goboatingnow]

Originally Posted by Dockhead

Cheaper? But they are much more accurate, aren't they? That looks like the way to go!

all satellite compasses should be similar as the maths used are similar hence the results. I would be surprised to see major difference between Simrad, Furuno and Hemisphere satellites compasses. Mind you Hemisphere are focused on the precision end of things

Dave

[barnakiel]

I would hold on and maybe soon you can get a less expensive GPS compass.

b.

[goboatingnow]

Originally Posted by barnakiel

I would hold on and maybe soon you can get a less expensive GPS compass.

b.

Why what do you know ?

Dave

[Dockhead]

Originally Posted by goboatingnow

all satellite compasses should be similar as the maths used are similar hence the results. I would be surprised to see major difference between Simrad, Furuno and Hemisphere satellites compasses. Mind you Hemisphere are focused on the precision end of things

Dave

Well, the claimed accuracy of the Hemisphere systems is an order of magnitude greater than Furuno. Whether it's really so or not is another question, I guess.

I have a friend who manufactures industrial GPS equipment in Moscow using the Glonass system. His stuff is accurate to millimeters -- he claims -- and he sells it for high precision applications like automated road grading and precise measurement of the sway of skyscrapers in the wind. I believe that the technical possibilities of satellite navigation vastly exceed our imagination.

I definitely feel a high precision satellite compass in my future