Interpolated Bounding Values using SteppedInterpolation

Hi Everyone

I know that Canary can do Simple Bounding and Interpolated Bounding when it's aggregate some time series.

I supuse that it use SlopedInterpolation method (described by the OPC Foundation https://reference.opcfoundation.org/Core/Part13/v105/docs/3.1.8 ), and I think that is the simplest and natural way to calculate bounds (just a straight line between know data).

I would like to explore the SteppedInterpolation (on the same link the explanation). But in simple words, is just take only the last known TVQ before the bound timestamp.

Is there any way to do that on aggregations?

Can I do some calculation every minute and save in the same origin tag the value at 00:00 seconds?

Thank you!

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  • Hi rodrigopoyanco ,

    Our aggregates use the SteppedInterpolated method described in this article with the exception of our Interpolative aggregate which uses the SlopedInterpolated method.

    I'm not sure I understand your question at the end though. Can you clarify?

    • Hi Steve , thank you for your reply

      I read on Canary documentation the following:


      Simple Bounding Value - uses the data points immediately before and after the boundary timestamps to estimate the bound, even if these points carry a 'Bad' data quality.

      Interpolated Bounding Value - uses the first non 'Bad' quality data points found before and after the timestamp to estimate the bound.


      What I understand from this, is that both methods take 2 data points: the before and after, and then (using SlopedInterpolation, in fact a straight line between the two data points), estimate the bound. The only difference between two methods are the treatment of Bad Quality data.

      In SteppedInterpolation, on OPC Foundation documentation, they says:

      Interpolated Bounding Values using SteppedInterpolation are calculated as follows:

      • if a non-Bad Raw value exists at the timestamp then it is the bounding value;
      • find the first non-Bad Raw value before timestamp;
      • use the value as an estimate of the bounding value.

      As you can see, in this case they only use one data point, the data before. In fact, it isn't an Interpolation, they use only the last known data point.


      It's clearer now my question? 

      Thank you again!


    • rodrigopoyanco 

      I think your understanding is correct. SteppedInterpolation uses the first value before the timestamp as the bounding value (if no value exists on the timestamp) and does not interpolate with the first value after the timestamp.

    • Steve Mason Thank you

      Ok, so Canary's Interpolation isn't Stepped, because it use the data before and after. So....is possible to do some Stepped Interpolation in Canary's aggregations? Or, Can I do some calculation to do this?

    • rodrigopoyanco 

      Canary does use SteppedInterpolation for all of its aggregates except for our Interpolative aggregate. It's the only one that uses SlopedInterpolation.

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