Cumulus Support

steve wrote:

mcrossley wrote:Hi Steve, yes it's the average speed. I haven't had a chance to examine it yet, but the average seemed to only be a little below the gust during the catch up and it broke my all-time record.

Yes, it's because the station-calculated average isn't available in the logger data, and the Cumulus calculation has very few samples to work with - it depends on your logger interval, e.g. with a logger interval of 10 minutes it only has one sample to calculate it from. At best it has 10 samples, with a 1-minute logger interval.

I've been thinking about this some more, as I now have the wind sensors in a more sensible place, I can switch have switched to using the VP2 average wind speed (and changed to integer values). Does this now mean that on future 'catch-ups' from the logger that Cumulus will read the average from the VP2 logger and avoid the issues I had last time?

As an aside I see that the Davis 'Green Dot' logger encryption code has now been broken opening up the market for third party loggers again. That was an exercise in futility from Davis and just upset lots of their customers.

mcrossley wrote:I've been thinking about this some more, as I now have the wind sensors in a more sensible place, I can switch have switched to using the VP2 average wind speed (and changed to integer values). Does this now mean that on future 'catch-ups' from the logger that Cumulus will read the average from the VP2 logger and avoid the issues I had last time?

No, this is what I meant when I said that the same information isn't available from the logger compared to running live; the 10-minute average speed isn't in the logger data. The logger data has the current 'instantaneous' (i.e. 3-second) speed at the time the logger entry was made, and the highest value of that item which occurred during the logger interval. So Cumulus uses the 'current' value for the speed, and that highest value for the gust. It then either uses that 'current' value directly, or in the average calculation, depending on the option setting, just as it does when running with 'live' data.

So in general, it does make sense to use the station value for the average, as the station can guarantee to use all of the available readings in the calculation, but it does mean that from logger data the average figure is just that one 3-second reading. I suppose there could be a 'hybrid' option - use station average when 'live' and calculate when using logger data, but unless you have a logger interval of less than 10-minutes, it wouldn't make any difference anyway, and even at lower logger intervals there's no guarantee that it would produce noticeably better results. In some circumstances it might make things worse. I think.

Thanks Steve, best thing is to try and avoid any outages and never have to clean up the data in the first place!

My newly sited wind sensors seem to be correlating with Ray's in Cheadle Hulme quite well...

mcrossley wrote:Thanks Steve, best thing is to try and avoid any outages

That's probably easier for you than for me We've had three power outages this month already, and with gusts of 70 mph expected this afternoon, we might have another one...