Chart is turning

[Princess]

As soon as I connect a heading sensor to my TZT the chart starts to turn back and forth and follows the heading data that is not stable. I have tested two different heading sensors with the same results, I have also disconnected all other sensors but the problem is still there.

 

[Melville]

That is because you are set to heads up chart display. Touch the little compass icon on the lower left and set it to north up.

 

[Princess]

Thank´s but that don`t make any difference, I have the same issue on my TZT14 and TZT9, I have the latest software 5.01. The heading sensors I have is WS200 and then I bought a second one just to try to find out what the problem is, Garmin Steadycast (not the best one maybe, but anyway) the problem starts as soon as I connect them to the system. I have also tested to turn off the PGN for heading in WS200 (Actisense NGT1) then it stops. As far as I can understand everything depends on the heading signal.

 

[Melville]

You're using GPS for heading which is not stable when not moving. Heading and course over ground are different.

 

[Princess]

Yes I understand but Steadycast don´t have a GPS it´s just a heading sensor.

 

[Melville]

When you call up heading display is it stable?

 

[Princess]

I´m not sure what you mean.

 

[Melville]

Select Heading for one of the databox displays. When tied to the dock does it remain steady?

 

[Princess]

I have connected everything at home, no movement at all but the heading is "jittering" 1-2 degrees up and down and the chart is following the heading. In rough sea it gets worse and it´s almost impossible to use the chart plotter.

 

[Melville]

no movement at all but the heading is "jittering" 1-2 degrees up and down and the chart is following the heading. In rough sea it gets worse

I am not familiar with the Garmin Steadycast, but if you are getting motion from the compass on the kitchen table it would be worse on a boat. When in heads up or north up mode the chart is reacting to the changes in heading. Is there a way to dampen that compass?

 

[Princess]

No unfortunately not, only in the TZT. I must set the dampen to atleast 15 sec to make it stable. For me it looks like there´s something about how the TZT handles the signal, PGN 127250 but that´s just my guess.

 

[Taniwani]

Sounds like you might have some electromagnetic interference from nearby appliances in your home.

 

[Johnny Electron]

Princess

If you are talking about COG, it isn't considered valid information unless you are moving 3 knots or better. If you are talking about heading, then it depends on the quality of the source information. I agree with Taniwani, that if you have a flux gate compass that is having problems with electromagnetic interference or big metal it will cause problems like you describe. You might want to have your dealer look into this further.

 

[Princess]

The reason why I tested at home was that I had the same problem in my boat. I also bought a new heading sensor but the problem is still there.

 

[Taniwani]

Princess,

this is getting confusing and I'd like to help you, but we need to clarify a few things that aren't clear to me from what you have written so far. So I'll ask a few questions to clarify what exactly you think isn't working as you would expect, and then see what can be done.

(1) Orientation: You say your chart display is wildly moving as soon as you connect a heading sensor. Your display allows for two orientations of the chart, North Up or Head Up. At some point in this post you seemed to say, that it doesn't matter what orientation you select, that chart will be moving. In North Up mode the chart display should be entirely unaffected by what ever heading information comes in for the heading sensor. So if you cannot switch the display to steady North Up when a heading sensor is connected, that would be a problem with the MFD and we would have to investigate down that path.

(2) Assuming that is is indeed possible to switch to North Up and get a steady chart display, but the heading of the ship icon keeps changing, and in Head Up mode the chart keeps turning left and right, we have to assume that the heading information that comes in from the sensor is changing frequently and the display just does what it is supposed to do, namely keeping the chart aligned with the heading. Then the question is: Should he heading actually change this much and for what reason or is this normal for any heading sensor.

One answer I can give you to that is that I have just traced my heading sensor and it emits the same heading of 46.6 ten times a second with absolutely no change in the value. And that is, what I would expect from a heading sensor if the boat doesn't move at all.

And I'm sure my display would act up if my sensor would send out changing headings. (Though I never use Head Up on the chart).

If you turn on a digital heading display on your MFD, you could see the heading that is being received and if it is not steady we'd have an idea where to look.

There are several possible things to check, but first we should see what of the above is true and not.

Harald

 

[Princess]

Thanks Harald, I´m grateful for all help. I have tested once more and I´m sorry I was wrong about that the chart is jittering when I use North up, it´s stable but the heading vector is jittering instead. The heading is changing at least plus/minus 1 degrees although the heading sensor lays still on the table. I really want to use heading up.

 

[Taniwani]

Hi Princess,

great, that narrows it down quite a bit. I would say that the MFD is probably fine, but it is receiving varying headings from the sensor. You mentioned two different sensors, a Garmin Steadycast (which to my knowledge has only a NMEA 2000 connection) and some other sensor that you seem to bring in via an Actisense gateway. Is that right?

I assume that you are not using both sensors at the same time, as that could leads to alternating different headings.

So try a sensor at a time, then, as you have it on your tale at home, turn the sensor slowly through 360 degrees and watch if the heading on the MFD follows. If it does and you find that depending on the direction it points the jitter gets less or more, then it is likely an interference. Note that the typical heading sensor sends out the heading 10 times or more per second, but in the stationary case, where the sensor isn't moving, all sends should show the same heading. For my sensors this is definitely true.

The sensors do no smoothing on purpose as they should report any any changes in heading as instantly as possible to stabilise the display of radar targets on the chart and on North up displays. The chart orientation in head up mode however could bee smoothed quite long as it just needs to display approximately with the general direction up. For that purpose, some MFDs have a course up option that can be active while going towards a waypoint. If your boat then meanders around a bit, the chart stays aligned to the active waypoint ahead.

That said, on a docked boat or the sensor on your kitchen table should result in a steady heading, that doesn't need any smoothing.

It is hard to imagine, that your sensor is sending out a stable heading and the MFD 'invents' the variations. And since the data transmission is checksum or CRC protected it is also not likely that the data gets corrupted on the way.

So it seems that your sensor is indeed seeing some changes in the magnetic field. Normally interfering fields that come from a stationary source would need to change in strength to cause a varying effect on your sensor. But that also means that the amount of variation you see would change with the orientation of your sensor. That's why I suggested to try turning the sensor.

Harald

 

[Princess]

Hi Harald!

The other sensor is Airmar WX200 same as Furuno WS200 (NMEA2000). I bought the Actisense NGT1 just to be able to read data from the system and try to find out what´s wrong. Only one sensor at same time, I can´t see any differens in jittering when i turn the sensors around. I read somewhere that there was someone else how had the same problem after update to 5.01. I tried to get back to 4.21 but the problem was still there so I went back to 5.01.

 

[Taniwani]

Hi Princess,

you say you have a NGT-1, that's good as you can check the heading output of the sensor to see if it is stable.

Look at the PGNs 127250, you should see many of these, about 10 per second. Compare them if you see any change in the data. They should all look the same. If not we would need to look towards the sensors, if they all have the same content we need to look at the MFD.

If you prefer, you can record an .ebl log with NMEA-reader and post it to me and I'd be happy to check it out.

Harald

 

[Princess]

Thank´s, I'll be away for a few days and will be back on Thursday then I try to record an .ebl log.