Clarify connection between UNC use of word “observation” and the GUM's “measured values”

[shunt16]

From Zhav Loizeau's review in #1:

I think there is an implicit choice about the word “observation” that is used to name what is called “measured values” in the GUM.

Issue to clarify this connection in the specification

[shunt16]

Agreed, will implement

[EmmaWoolliams]

This isn't easy. There is a strong disagreement about what "observation" means - see my paper with Peter Strobl, and the whole conversation about observation in its section 3.3.1:
https://link.springer.com/article/10.1007/s10712-024-09854-8

What we recommend in there, is to treat this as what we call a "controversial term" and acknowledge the controversy while also making it really clear what you mean by observation.

[EmmaWoolliams]

Also, building on comments from me and Peter Harris:

We have to be careful with both measurement and observation:

a) to distinguish them - or declare them synonyms. See my paper with Peter Strobl and my new paper.

b) Observation / measurement are nouns to describe a process - you make an observation and take a measurement meaning that you go through a series of steps with a sensor.

The output of such a process is a measured value or an observed value - again my paper with Peter Strobl describes this.