Sampling rate changes for graphs

[VK6TNC]

Over time the displayed graphs change their sampling rate. The lines change from smooth to a series of steps. Looks like the sampling rate halves for some reason.

Restarting Cumulus seems to cure this. Has anyone had the same problem?

Chris

[steve]

When plotting "live", Cumulus plots at 1-minute intervals. When it starts up, it builds the graph history from the data in the log files. This may have been plotted at your station logger interval or Cumulus logger interval, depending on how that data was obtained (this is one reason I recommend having them set the same). This is why the sampling rate changes, and is one reason for the graphs looking different over time.

However, this may not be the cause of what you are seeing. I've also noticed a slight 'stepped' effect being introduced occasionally, even when all of the graph has been plotted from live data. I think it's an issue with the chart component - there's certainly nothing that Cumulus does that could cause this. Of course, you would always expect to get a slightly stepped effect if the data only has discrete values, e.g. the wind speed with the Vantage Pro is reported to the nearest mph, and I believe the Fine Offset stations only report certain values, even though this isn't mentioned in the spec.

The next beta build of Cumulus will be using a new version of the charting component, so if what you're seeing isn't explained by the change in sampling rate, and there is an issue with the component, it's possible this one will have fixed it. There's also a option to have a 'smoothed' line, which I quite like, so I'll look into offering this as an option.

[VK6TNC]

Thanks Steve,

Data is logged at 15 min intervals in the console and Cumulus. Weather.txt is uploaded every 60 seconds. You can see the effect on my website www.vk6tnc.cz.cc I restarted the software just before 10:00am today.

I too believe it to be a quirk in the charting software and look forward to the next beta.


Chris

[steve]

That effect currently on your wind graph is because of the difference in plotting intervals between "live" data and logger data. The stepped effect on the "live" part of the gust line is because by default that line plots the 'peak gust in the last 10 minutes'. If you don't want it to plot that value, you can change it to plot the latest gust value from the station by using the 'plot latest gust' setting in the display settings.

[VK6TNC]

Changes done. Looks better now.

Thanks for the info