Expedition Navigation Software 
1 of 1- ZigZag
- Expert
Offline - Registered: 7/29/2019
- Posts: 16
Nexus Instruments data transfer using TBS/CAD/CFD data fields
When I setup Expedition to send the "Bearing to Mark" data from the Expedition S/W to the Nexus Multi Control Instrument using the (NMEA) CAD data field I get these results:
a) Nexus Instruments set to Magnetic, Expedition set to True. The CAD value will show the correct magnetic mark bearing value on the Nexus Instrument.
b) However, when I set Expedition and Nexus Instruments to Magnetic, the CAD value shown on the Nexus Instrument is incorrect (offset by the current magnetic variation set in the C33 calibration value).
Thus, It appears that either Expedition doesn’t send info if it sends Magnetic or True values via the NMEA I/F or the Nexus instruments always assumes the CAD values to be True. Any way to fix this? I would like to utilize Magnetic values both on Expedition S/W and on the Nexus Instruments.
- Nick
- Moderator
Offline
- Registered: 9/16/2015
- Posts: 2,966
Re: Nexus Instruments data transfer using TBS/CAD/CFD data fields
If Exp is in true mode, it should send the value in degrees true.
You can see the value sent on the raw data window
- ZigZag
- Expert
Offline
- Registered: 7/29/2019
- Posts: 16
Re: Nexus Instruments data transfer using TBS/CAD/CFD data fields
Nick,
you're correct. When Expedition is set to degrees true, the data will be send in degrees true and the Nexus Instruments applies the Magnetic Variation to then display the value as degrees magnetic. All is well.
However, when Expedition is set to degrees magnetic, the data that is being send by Expedition still gets adjusted by the Magnetic Variation and the degrees magnetic display on the Nexus Instruments is off by the Magnetic Variation. Thus, either Expedition doesn't transmit if it sends degrees true or degrees magnetic data or the Nexus Instruments don't correctly interpret that data. In any case, the Magnetic Variation will be applied regardless of Expedition being set to Magnetic or True degrees.
Last edited by ZigZag (8/13/2019 9:47 am)
- •
Thread Starter- Nick
- Moderator
Offline
- Registered: 9/16/2015
- Posts: 2,966
Re: Nexus Instruments data transfer using TBS/CAD/CFD data fields
I didn't know that. There isn't anything in the documenation. I will ask ...
- Nick
- Moderator
Offline
- Registered: 9/16/2015
- Posts: 2,966
Re: Nexus Instruments data transfer using TBS/CAD/CFD data fields
It turns out that magnetic variation is applied to CAD in old Nexus hardware, but not in Garmin systems.
So, I am not sure what the solution is ....
Are you using the FDX or NMEA connection?
Last edited by Nick (8/14/2019 1:40 pm)
- Joe Goulet
- Expert
Offline
- From: Fort Lauderdale, FL USA
- Registered: 9/16/2015
- Posts: 83
Re: Nexus Instruments data transfer using TBS/CAD/CFD data fields
On one boat that I race GPS data is obtained from a Garmin 1040 GPS/Chart Plotter that, for one reason or another, will only transmit COG in magnetic, which forces us use magnetic throughout our navigation systems. In that boat's Nexus system I use the FDX connection and in order to get the Nexus magnetic HDG to agree with the Expedition magnetic HDG I set the correct magnetic variation in Nexus and then set an opposite value in Expedition (Exp cals - Hdg [check the box then set the value]).
My thinking (quite possibly flawed) was that Expedition was obtaining the magnetic variation value from the chart and combining / compounding it with the magnetic HDG obtained from Nexus (which might be incorrectly identified by Nexus in the transmission) to produce a magnetic HDG with a doubled magnetic variation.
After performing the massage described above I check to insure that Nexus and Expedition are producing the same magnetic HDG and then check that number against what is shown with a handbearing compass.
There is probably a better way of dealing with the issue and I am open to suggestions which might reflect an accurate conceptual understanding.
- ZigZag
- Expert
Offline
- Registered: 7/29/2019
- Posts: 16
Re: Nexus Instruments data transfer using TBS/CAD/CFD data fields
Joe,
interesting. I'll check next time I'm on the boat over Labor Day weekend. I thought that I was sure that the Magnetic Heading on the Nexus instruments agreed with the Magnetic Heading on Expedition when I set Nexus instrument Expedition S/W to Magnetic degrees in the Settings (w/o your "special"adjustment in Expedition). I'll verify and post the results. I'm certain that the Nexus Magnetic Heading does agree with my compass readings.
I only noticed the difference between the Bearing to Mark Magnetic values displayed in Expedition vs. that value on Nexus after it was transmitted using the Expedition CAD data field.
- •
Thread Starter- Nick
- Moderator
Offline
- Registered: 9/16/2015
- Posts: 2,966
Re: Nexus Instruments data transfer using TBS/CAD/CFD data fields
We (Garmin and myself) think we have a solution for the next Exp update.
- ZigZag
- Expert
Offline
- Registered: 7/29/2019
- Posts: 16
Re: Nexus Instruments data transfer using TBS/CAD/CFD data fields
Nick,
that would be great! Could you please advise on the estimated implementation date and what is required to make it work.
Also, could you please let me know if there is any way to automatically adjust the magnetic variation value in the Nexus Instruments w/o having to update the calibration value (C33)
- •
Thread Starter- Nick
- Moderator
Offline
- Registered: 9/16/2015
- Posts: 2,966
Re: Nexus Instruments data transfer using TBS/CAD/CFD data fields
Unfortuntely, there is no eta for the release, but I can give you the pre-release build if you wish. Just email me.
I don't know enough about Nexus to answer that sorry. There may be an option in their Nexus race software?