Request for input to the BP doc: an introduction to CRSs and related concepts

Hi-

Thinking about the article that I just shared [1] on the mailing list it
occurs to me that to the majority of webby folk, coordinate reference
systems, projections, datums and the like will seem like some kind of dark
art ...

All they will be used to is what every global mapping provider uses: spherical
/ web mercator EPSG:3857 [2] “google maps projection”

And likely they don't give it any thought at all.

Much in the same way that I have introduced features / spatial things and
geometry in the front material of the SDW BP doc [3], I think we need a
_short_ section to introduce the topic of coordinate/spatial reference
systems (including non-earth CRS; e.g. cartesian used in
imagery/microscopy) and projections so that readers:
1. know what the terms mean (a little bit - point them to references if
they want to find out more)
2. why it matters

Please can a member of the Working Group provide a paragraph or two- and
better still do it in GitHub and create a Pull Request with your proposal?

I'm thinking that this might be right up @eparsons' street (no spatial pun
intended). I also recall that I've recently had conversations with @josh
about CRS.

Please help.

Best Regards, Jeremy

(who is still thinking about work while I'm trying to pack holiday
suitcases!)

PS: I also note that the section I have written on spatial references [4]
is a little underwhelming. If anyone fancies re-working that section, I
would appreciate it very much!

[1]: https://lists.w3.org/Archives/Public/public-sdw-wg/2016Jul/0336.html
[2]: https://epsg.io/3857
[3]: http://w3c.github.io/sdw/bp/#spatial-things-features-and-geometry
[4]: http://w3c.github.io/sdw/bp/#spatial-relations