UCR ISSUE-70: add a requirement for avoiding coordinate transformations?

Hello all,

This message is to make a thread dedicated to ISSUE-70
<https://www.w3.org/2015/spatial/track/issues/70>

The need to perform coordinate transformations occurs when spatial data
(geometries and coverages) from different sources need to be combined and
the data use different coordinate reference systems.

There can be several reasons for wanting to combine spatial data from
different sources:

   - visualisation in a desktop app or web app
   - storage in a data store that is configured for a single CRS
   - federated SPARQL queries
   - more?

Coordinate transformations take time and could introduce errors in the
output, so it is preferable to avoid them. A requirement could call for
recommendations for publishing spatial data on the web in such a way that
there is less chance of data consumers having to perform coordinate
transformations.

Questions I would like to put to you:

   - Is this a sensible requirement?
   - To which deliverables should the requirement be related? Best Practices
   and Coverages too?
   - Does the requirement follow from other use cases besides Combining
   Spatial RDF Data For Integrated Querying In A Triplestore
   <http://w3c.github.io/sdw/UseCases/SDWUseCasesAndRequirements.html#CombiningSpatialRDFDataForIntegratedQueryingInATriplestore>
   ?

Regards,
Frans