Wind Speed Options

[nking]

I have got myself confused by the various wind options. Within station settings there is calculate 10 min average which I believe relates to gust speeds, however, I can also select wind speed if I want the average based upon wind speed rather than gust i.e. both ticked. What would happen if only wind speed were ticked?

If I choose to use AvgSpeedMinutes=15 for example in the ini file, do I need to have either or both of the station settings ticked? I’m unsure which takes precedence I guess there is no option to alter the 10 min average gust speed?

[steve]

Ticking 'Calculate' turns on the option to get Cumulus to calculate the average wind speed. Without that, none of the other settings have any effect as the value is then simply read from the station.

The default when 'calculate' is ticked is that Cumulus uses the 'gust' value (or whatever the equivalent is depending on the station type - it's the value that appears in Cumulus as 'latest') to calculate the average. With 'use speed' ticked, it uses the 'other' wind value supplied by the station (whatever that happens to be depending on the station type).

The AvgSpeedMinutes value overrides the default 10 minute setting for the period over which the average is calculated. It is independent of whether the 'use speed' setting is ticked or not.

I don't understand the question about altering the 10 min average gust speed, could you clarify?

[nking]

Ticking 'Calculate' turns on the option to get Cumulus to calculate the average wind speed. Without that, none of the other settings have any effect as the value is then simply read from the station.

OK

The default when 'calculate' is ticked is that Cumulus uses the 'gust' value (or whatever the equivalent is depending on the station type - it's the value that appears in Cumulus as 'latest') to calculate the average. With 'use speed' ticked, it uses the 'other' wind value supplied by the station (whatever that happens to be depending on the station type).

OK

The AvgSpeedMinutes value overrides the default 10 minute setting for the period over which the average is calculated. It is independent of whether the 'use speed' setting is ticked or not.

This is where I was confused. I had interpreted AvgSpeedMinutes to only apply to the ‘other’ wind value (F/O is wind speed) and not the one as ‘latest’ (F/O is gust speed).

I don't understand the question about altering the 10 min average gust speed, could you clarify?

Based upon my misunderstanding of AvgSpeedMinutes you may have guessed that you have answered my questions.

It may only be me being thick but my understanding became clouded by the terms Gust Speed and Wind Speed (especially relevant with F/O’s). I suspect your eloquent clarification should be placed in FAQ’s.

[steve]

It may only be me being thick but my understanding became clouded by the terms Gust Speed and Wind Speed (especially relevant with F/O’s).

It's the old problem of different stations measuring different things and naming them differently and what is a gust anyway and...

I suspect your eloquent clarification should be placed in FAQ’s.

Yes, probably. The documentation is a bit lacking because of the way the extra options have just been tacked on, and one of them being 'hidden' by being an ini-file option.

[daj]

There are a few possible combinations there based on what your station is. Steve, I wonder if you could list what each station supplies on its own, based on your knowledge of the different types of station. I could only comment on my own so i am not the best person to produce this!

[steve]

I really only have limited knowledge of the details of each station, so this is the best I can do (and some of it may well be wrong). Bear in mind that given the way these stations measure wind speed, all the values are an average of some sort, as all they do is count revolutions over a given period and convert that to a speed. Rather than use confusing terms like 'gust', I'll just call them "speed 1" and "speed 2". If you don't have Cumulus set to calculate an average, Speed 1 = "Latest" and Speed 2 = "Average". If you do have Cumulus set to calculate an average, speed 1 is used in the calculation if you don't have the 'use speed' option ticked, and speed 2 is used if you do.

Fine Offset
Speed 1: Some sort of peak value over the previous 48 seconds
Speed 2: Average over previous 48 seconds

Davis
Speed 1: Average over previous 3 seconds
Speed 2: Average over previous 10 minutes

Oregon Scientific
Speed 1: Average over previous 14 seconds
Speed 2: Don't know. Presumably an average over a longer period.

La Crosse
Only supplies one wind speed. I don't know how it's calculated.