Dashboard - Mag Heading

[rgleason]

Today while VDR recording, using opencpn v 4.8.0 our dashboard value for Mag Heading was 999. I am assuming that is because our Autopilot was not turned on and thus the fluxgate was not sending.

If this is in fact true, perhaps we should add a note about that in the Dashboard documentation?

[transmitterdan]

Originally Posted by rgleason

Today while VDR recording, using opencpn v 4.8.0 our dashboard value for Mag Heading was 999. I am assuming that is because our Autopilot was not turned on and thus the fluxgate was not sending.

If this is in fact true, perhaps we should add a note about that in the Dashboard documentation?

Rick,

It should display --- instead of 999. I will look into it.

999 is the default for data not yet received over NMEA. So yes, it is caused by having no heading data from NMEA stream.

[rgleason]

Thanks TDan. Will be running it tomorrow and VDR recording. Have turned of magnetic and saw no change.

[transmitterdan]

Magnetic COG comes from GPS not fluxgate but is supposed to be corrected from true based on local variation.

Magnetic Heading comes from fluxgate or other heading sensor.

GPS based course values can be optionally filtered. Magnetic sensor readings are not filtered by O.

[transmitterdan]

Rick,

One further note on this. The Mag COG value is computed using the variation as delivered from the GPS via NMEA. It does not use the variation from the WMM plugin or the user entered value for variation in the Options->Display->Units dialog.

[rgleason]

Ok, Magnetic Heading is from the fluxgate electronic/digital compass and it appears when there is no such nmea sentence, the value issued is "999". How hard would it be to have it show alphanumeric, "Fluxgate compass off"?

Also today while comparing a B&G screen and Opencpn screen with similar active routes, it became clear that OpenCPN has something wrong with the heading indicator. It always seems to be pointing to the right too much. When compared with the B&G display this becomes really noticeable.

See the two attached photos. In this area the magnetic variation is about 14 degrees. It appears the heading indicator has an incorrect use of magnetic variation, even with wmm plugin enabled, and with all variations of Show magnetic. Show true. And with both true and magnetic shown! It does not seem to do anything to the heading vector angle. I am thinking that the heading is calculated separately from the other features.

It would be nice know what this is caused by, and how to correct it.

Hope the photos help. Attached next

[transmitterdan]

Rick,

I would need a VDR file to tell you why the angles are what they are.

[rgleason]

Great. I will attach today's vdr file hopefully compressed.

[rgleason]

Could this problem be related?

[transmitterdan]

Originally Posted by rgleason

Could this problem be related?

What problem is related?

[rgleason]

Posted it under wrong topic...
I <br />
Sorry, this one.<br />
http://www.cruisersforum.com/forums/...d.php?t=169005<br />
<br />
Will try to upload VDR tomorrow morning.

[rgleason]

Dan,
Yesterday, while on a long motor using too much F.Fuel, near Newport, I turned on and used the autopilot and fluxgate compass. (- I think I should power the fluxgate on from the chartplotter now, as I have never had a chartplotter before.. and O can use magnetic heading).

Anyway the Mag HDG went to something sensible, and I got COG and heading vectors that finally made sense to me.

I am including the VDR file of that leg and a photo.

I am wondering why we have:
COG Predictor Length (Min) 15
Heading Predictor Length (NMi) 1

These predictors with different UNITS (Time & Length) I think it would be better if they were the same.

[transmitterdan]

COG predictor line is in units of time because that typically indicates how far out we should be concentrating and it should also remind us that further out than that the situation will change before we get there. The radius of concern changes with speed (faster means we have to concentrate on a larger radius from the boat) thus the length of the COG line is based entirely on vessel speed.

Heading shows us how the vessel lies relative to course. But since a sail boat is often not traveling in the heading direction there is little point in adjusting that line as a function of speed. It would give the false impression that the near term destination lies at the end of the heading line. The near term destination lies always at the end of the COG line.

[transmitterdan]

Originally Posted by rgleason

Dan,
Yesterday, while on a long motor using too much F.Fuel, near Newport, I turned on and used the autopilot and fluxgate compass. (- I think I should power the fluxgate on from the chartplotter now, as I have never had a chartplotter before.. and O can use magnetic heading).

Anyway the Mag HDG went to something sensible, and I got COG and heading vectors that finally made sense to me.

I am including the VDR file of that leg and a photo.

I am wondering why we have:
COG Predictor Length (Min) 15
Heading Predictor Length (NMi) 1

These predictors with different UNITS (Time & Length) I think it would be better if they were the same.

Rick,

Something is wrong with this boats electronics. The GPS is sending coordinates and speeds that are obviously wrong. In the VDR file there are speeds in excess of 100 knots and position changes of many hundreds of miles. Here is a shot of part of the track log. It shows crazy positions and velocity calculated therefrom.

[rgleason]

That's puzzling. The gps used is from the B&G Zeus 12 Touch, built-in. It has been quite reliable in getting us to our destinations.

I have Raymarine Seatalk instruments which are connected to the B&G Nema2000 bus with a Raymarine Seatalk/SeatalkNS converter and the output is wired directly to the Nema2000 bus. The ZeusT12 shows wind and instrument data from this.

I have a gps puck wired directly to my nmea0184 input on the DSC VHF, which is totally independent from the B&G & instruments.

I have another Win10 bu353 gps puck that I use with my MS Surfacepro3 and OpenCPN, but I removed that because I had gps from the B&G which was running. At first I was getting a double signal.

The way I get data into opencpn is via a german gadgetpoole seatalk link, to nmea01823 with serial converter to usb plugged into the single usb port on the surfpro3. I did not have to use my usb/ethernet hub because I did not need the Gps puck or ais.

The other end of the gadgetpoole seatalk link is directly connected to the three seatalk wires, but the device is galvanically isolated and powered from a 12vdc fuse and breaker. This bidirectional device is set up to not duplicate data already available.

The Raymarine Seatalk/seatalkNS converter is probably putting the ZeusT12 GPS signal onto the Seatalk bus and the gadgetpoole seatalk link is getting it to opencpn as nema0183 data.

The last day I turned on my autopilot. Was the 100mph seen before or after that? Was this found on a consistent basis?
I recall several times when O failed and I had to restart, that the boat was located far away and there was a red line off the screen for moment before the new gps signal came through.

Could this be what happened or is it more frequent than that?