Expedition Navigation Software 
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- themisl
- Member
Offline - Registered: 10/17/2023
- Posts: 4
Difference of True Wind Angle in Expedition and on the B&G FFD display
Hi,
I recently discovered a strange behaviour of the True Wind Angle function that appers on Expedition Screen.
Every information i read on Expedition is the same as on the FFDs or the 20/20 displays of a B&G hydra 690 system with performance processor.
However i have a difference of at least 4 degrees on the true wind angle that is displayed on the FFD, and the one appearing on the Expedition box, when we sail Upwind. The problem disappears when we sai downwind. Having noted that, I suppose this has something to do with the Leeway or with True Wind Angle calibrations or corrections that Expedition does. So i tried unchecking every box i found in the settings, but the problem still remains.
Has anyone encountered such a problem in the past?
Any help would be mostly appreciated.
- sparky
- Expert
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- From: Cambridge UK
- Registered: 4/27/2018
- Posts: 246
Re: Difference of True Wind Angle in Expedition and on the B&G FFD display
How is expedition connected to the system?
The few things that jump to mind --- check the TWA source in the B&G system.
Double check you don't have the True Wind calculation turned on in Expedition.
Check the BSP settings in the B&G and Expedition --- one might be using SOG as BSP...
- themisl
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- Registered: 10/17/2023
- Posts: 4
Re: Difference of True Wind Angle in Expedition and on the B&G FFD display
Hi, thanks for the reply.
Expedition is connected through a Rs232 to USB cable.
I have also thougth about True Wind calculation in Expedition, which is turned off.
I also checked BSp setting in the B&G and it set to BSP. in Expedition I rememeber seeing such an option somewhere in the software but i don't remember where exactly. I will check it again.
When you say "the TWA source in the B&G system" what do you mean? Which can be the source either than the processor?
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Thread Starter- themisl
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- Registered: 10/17/2023
- Posts: 4
Re: Difference of True Wind Angle in Expedition and on the B&G FFD display
I remembered where the SOG option is. It is in the B&G H690 / H2000 Perf Connection Menu under the option B&G H690 / H2000 Perf Settings/ ExpCalcs. I had never checked any box there.
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Thread Starter- sparky
- Expert
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- From: Cambridge UK
- Registered: 4/27/2018
- Posts: 246
Re: Difference of True Wind Angle in Expedition and on the B&G FFD display
I'm more familiar with the H5000... In the H5000 you can select the raw data from an instrument or calculated value from the computer for certain things... you can also add dampening and calibration.
Do the values either on the displays or in expedition match the un-calibrated values? I remember working on one system that the values being sent on the computer interface were "raw" values and the ones sent on the NMEA network were corrected.
- Nick
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- Registered: 9/16/2015
- Posts: 2,966
Re: Difference of True Wind Angle in Expedition and on the B&G FFD display
Exp just displays what is received from the B&G, unless you have selected calibration or calculation options (which you shouldn't in this case).
It could be leeway. H3000 tells Exp if it has leeway in it or not. If it doesn't, Exp adds it.
This wasn't available for H690-2000, so Exp assumes it needs to add leeway.
- themisl
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- Registered: 10/17/2023
- Posts: 4
Re: Difference of True Wind Angle in Expedition and on the B&G FFD display
Thanks Nick for the reply,
THis is also what i ended up with. Exp assumes it needs to add leeway.
However this leads to other problems:
It seems that Exp adds Leeway on starboard tack ( i have high TWA) and substracts Leeway on port tack (I have low TWA). My leeway value in Exp is always negative when i let it take into account the value that comes out of the intruments. When i click the option to calculate leeway, the leeway value changes sign in each tack. I assume that this relies on the sign of the heel value.
I am not sure if the sign (+ or - } of the heel angle plays a role on that. However my heel angle in EXP is negative on port and positive on starboard, while accoridnig to the manuals it should be "Heel (roll)
is positive to starboard (sailing on port)."
This whole situtation in so confusing when trying to calibrate TWA values....and also when trying to acheive target angles and VMGs.....
Last edited by themisl (7/09/2024 11:11 am)
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