WInd value and direction

[Dario Cillerai]

Hello, what is the wind speed reported in Current Conditions?

Is it the instantanoeus value or an average (for example, on the page  update interval) ?

I've a Davis Vantage Pro 2 and I think the value is an average because I may see, for example, 1 , 2, 3, 4 Km/h but this may not correspond to any value in miles per hour, which is the unit used by the station:

1 mph => 1.6 Km/h

2  => 3.2

3  => 4.8

...

Then, what is the interval for the average?

And, finally, what about wind direction?

Thanks and Regards,

Dario

[Tom Keffer]

For the VP2, the value of type "windSpeed" is whatever the console emits at the end of an archive interval. Generally, this is the average wind seen during the interval. Same with "windDir".

Similarly, "windGust" is whatever the Vantage emits, which is generally the maximum value seen in the archive interval. Same with "windGustDir".

By default, the interval is set by your console. You can change the value by either consulting your owner's manual and pressing the appropriate buttons on your console, or by using the WeeWX tool "weectl device" with the --set-interval option. 

I didn't quite understand your question about Km/hr vs mph. I think you're questioning the loss of decimal precision in the conversion? 

The Vantage emits wind speed in whole miles per hour, with no decimal. So, by default, the format used by $current.windSpeed rounds to the nearest whole number. Yes, it's true that converting, say, 3mph to metric is something closer to 4.8 km/hr, but it's also true that the Vantage does not have that kind of precision. It can't honestly measure the difference between 4.8 km/hr and 5 km/hr.

You can change the formatting by using a tag such as $current.windSpeed.format("%.1f"), but it's probably best not to claim more precision than there really is.

Hope that answers your questions.

-tk

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