Hi togehter,
I am wondering why campbell not offers a two passes (double-pass) method for calcluating the standard deviation for the wind directions.
The standard methods are only single pass methods for estimating the wind directions. (eg. Yamartino)
What are the reasons?
- the cpu power
Would be very usefull, if the next version of crbasic offers:
- wind direction standard deviation (two pass method)
- wind direction maxima value
- wind direction minima value
Greets moho
Normal two pass methods require buffering of the data for the entire period over which the data is collected before processing. It is for this reason these methods are not normally used for SD calculations as you can quickly run out of memory. The other disadvantage is that you need to do a lot of processing all at one time at the end of the interval rather than a little bit of the processing being done after each measurement.
If you want this feature though there would be nothing to stop you doing this currently in CRBasic. You'd need to buffer the data into an array which holds every measurement of direction over the chosen period then you can either use custom code to run through the array and calculate the SD or use the StdDevSpa, MaxSpa and MinSpa instructions to do the processing. It is unlikely the StdDevSpa will be suitable though as you need to cater for the issue with the direction moving through North (360 <-> 0 degrees).
Andrew