Re: UCR ISSUE-75: Coverage requirement for quality metadata in scope?

Hi Jon,

Thank you for your thoughts. It seems to me that your first point, quality
information for the entire dataset, does not really justify the explicit
requirement. It is something that should already be covered by general best
practices for data on the web, right?

But data quality data per sample value seems to be something that needs
specific guidance. By the way, is it OK to use 'sample' instead of 'pixel'?
Not all coverage data are raster data...

So how about rephrasing the requirement to "It should be possible to
describe properties of data quality (e.g. uncertainty) per data sample"?

By the way, are there other quality properties next to uncertainty that
should be possible to record per sample in a coverage? If it is only
uncertainty that matters, couldn't that be adequately addressed by using
significant digits?

Regards,
Frans



On 13 September 2016 at 20:31, Jon Blower <j.d.blower@reading.ac.uk> wrote:

> Hi Frans,
>
>
>
> I agree that data quality is a general issue. However, there may be some
> specific things to say about coverages. For example:
>
>
>
> 1.       “General” quality information (e.g. sensor accuracy) could be
> recorded as metadata with the coverage.
>
> 2.       However, if we want **per-pixel** quality information in the
> coverage, this implies that we need a set of range values for the quality
> information (e.g. one set of range values for temperature, and one for the
> uncertainty on the temperature, howsoever measured). It also means that
> there ought to be a way to link these two sets of range values together, to
> advertise to clients that they should consider those two things together.
>
>
>
> There are no widely-used standards for per-pixel quality information as
> far as I know, but we have proposed such a mechanism in CoverageJSON [1].
> In a previous project (GeoViQua) we developed a way to do this in WMS too
> [2]. Both are incomplete and could be further developed.
>
>
>
> (UncertML provides a vocabulary for probability density functions and
> statistics, which can be reused here.)
>
>
>
> Best wishes,
> Jon
>
>
>
> [1] https://covjson.org/spec/#parametergroup-objects
>
> [2] http://dx.doi.org/10.3390/ijgi4041965
>
>
>
> *From: *Frans Knibbe <frans.knibbe@geodan.nl>
> *Date: *Friday, 9 September 2016 14:57
> *To: *SDW WG Public List <public-sdw-wg@w3.org>
> *Subject: *UCR ISSUE-75: Coverage requirement for quality metadata in
> scope?
> *Resent-From: *<public-sdw-wg@w3.org>
> *Resent-Date: *Friday, 9 September 2016 14:57
>
>
>
> Hello everyone,
>
>
>
> I just realised ISSUE-75 <https://www.w3.org/2015/spatial/track/issues/75>
> did not have its own e-mail thread yet. Of course that won't do. So this is
> the official thread for ISSUE-75.
>
>
>
> The issue is about the quality metadata requirement
> <http://w3c.github.io/sdw/UseCases/SDWUseCasesAndRequirements.html#QualityMetadata>.
> It is a requirement for the Coverage deliverable. It currently reads "It
> should be possible to describe properties of the data quality, e.g.
> uncertainty."
>
>
>
> The need to describe data quality is a general data issue, so it does not
> seem in scope for the Coverage deliverable and perhaps it does not need to
> be mentioned in the UCR document.
>
>
>
> Should we decide to keep the requirement, perhaps it could just as well be
> related to the other deliverables.
>
>
>
> Is there something about coverage data that justify making this
> requirement explicit for the coverage deliverable?
>
>
>
>
>
> Greetings,
>
> Frans
>
>
>
>
>