Stream: implementers
Topic: SampledData - SimpleQuantity
Brian Reinhold (Aug 08 2016 at 10:31):
This does not look like a popular topic as a search on SampledData led to nothing. I am trying to map IEEE waveform data to an Observation and most of it is straight forward EXCEPT for the SimpleQuantity concept used in the SampledData. The 'origin' element is described as a SimpleQuantity with the description "Zero Value and units" with cardinality 1..1. But it is not clear to me what a SimpleQuantity is. The documentation says a fixed Quantity. How do I interpret this? If I have a zero value of 1.0 and a code system describing the unit, how is this represented? How does one interpret "SimpleQuantity"? Any one of the Quantity options?
Thanks for any clarification. (The example for an ECG contains no units, just a zero value.)
Grahame Grieve (Aug 08 2016 at 11:42):
http://hl7-fhir.github.io/datatypes.html#2.20.0.6.1. I see the reference to SimpleQuantity is a broken link.
Grahame Grieve (Aug 08 2016 at 11:45):
I'll fix taht
Brian Reinhold (Aug 08 2016 at 14:15):
Thanks. That might be all I need.
Brian Reinhold (Jan 06 2017 at 14:00):
Grahame,
Looks like I need a little bit more of a clarification on the SampledData 'origin' element. It is described as follows:
The base quantity that a measured value of zero represents. In addition, this provides the units of the entire measurement series.
It is not clear to me what 'measured' means. If I look at the scaleFactor element it is described as
A correction factor that is applied to the sampled data points before they are added to the origin.
Its the added to the origin that confuses me. Now what I would expect is that the origin.value element would be some constant to which the re-scaled data elements are added. Thus the actual MEASURED quantity is
original measured value[i] = valueSampleData.data[i] * valueSampledData.scaleFactor + valueSampledData.origin.value
Thus the origin is not the measured value 0 but the data value 0.
Is that correct? In other words is my above equation the correct one to get the original values? Thus uploading I would do
valueSampleData.data[i] = (original measured value[i] - valueSampledData.origin.value) / valueSampledData.scaleFactor
Thanks for any clarification.
Grahame Grieve (Jan 06 2017 at 20:39):
MEASURED quantity is
original measured value[i] = valueSampleData.data[i] * valueSampledData.scaleFactor + valueSampledData.origin.value
Grahame Grieve (Jan 06 2017 at 20:40):
yes. I agree that the wording is a little misleading; I tried to be too brief. can you make a task to clarify?
Last updated: Apr 12 2022 at 19:14 UTC
