True vs Apparent Wind Speed

[SV_Atlas]

Hello!

We have recently installed Saillogger on SignalK and are enjoying having a good tracker for our family back home.

I've noticed that the wind speed is Apparent, while wind direction is True. I would like to have the wind speed as True but when I make the change "environment.wind.speedTrue" I no longer have any wind data on our tracking page. If I change it back to "environment.wind.speedApparent" then the wind data reappears.

I have installed Derived Data but that has not solved the problem.

My only thought is that it appears Derived Data needs to have some sort of boat speed for it to derive the true wind speed. Is this correct? If so, I believe, then, that if we are anchor and the wind speed is set to True, then it will display a value of 0 until we move again.

Can you confirm if this is correct?

If so, may I suggest that there is both an Apparent and True Wind speed?

Thank you very much for building what appears to be a really great product.

[admin]

Hi there,

For true wind speed and direction, you should toggle the following option on in the derived-data plugin:

• True Wind Angle, Direction and Speed

In order to calculate true wind values, the following are required:

• navigation.headingTrue
• navigation.speedThroughWater
• environment.wind.speedApparent
• environment.wind.angleApparent

speedThroughWater should be coming from your speedometer, and when anchored, it will be zero, so no problems there. speedApparent and angleApparent come through wind instrument and should be fine too.

headingTrue is the tricky one, it normally comes through the heading sensor which is normally linked to autopilot but depending on your instruments, it may be sourced from elsewhere too. If you don't have all of these, derived-data will not be able to calculate the true wind readings.

You can see which ones are available in the data browser.

Good luck and happy Saillogging!

[SV_Atlas]

Done! Thank you very much. That was an easy fix and simply required power to my course computer.