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

From: Joshua Lieberman <jlieberman@tumblingwalls.com>
Date: Mon, 1 Aug 2016 12:28:21 -0400
Cc: Rob Atkinson <rob@metalinkage.com.au>, Linda van den Brink <l.vandenbrink@geonovum.nl>, SDW WG Public List <public-sdw-wg@w3.org>, Jeremy Tandy <jeremy.tandy@gmail.com>
Message-Id: <C70A90C0-7456-4E52-97DB-5839975E51BA@tumblingwalls.com>
To: Ed Parsons <eparsons@google.com>
Ed,

I’ll have a go at updating this if that’s alright with you. It seems to me it would be good to emphasize that spatial data users are usually projecting their data from WGS84, either explicitly (e.g. Web Mercator) or implicitly (e.g. haversine), in order to map or do calculations. So it may be more of a question of when to know what you’re doing to vary this, rather than projecting or not projecting.

—Josh

> On Aug 1, 2016, at 10:10 AM, Ed Parsons <eparsons@google.com> wrote:
> 
> Turns out you can't do it in a paragraph, here is my first attempt...
> 
> https://docs.google.com/document/d/1EO70CvPJWg_dWcmgrzElUQMe6IK5OTry5S291ALQoKo/edit?usp=sharing <https://docs.google.com/document/d/1EO70CvPJWg_dWcmgrzElUQMe6IK5OTry5S291ALQoKo/edit?usp=sharing>
> 
> Feel free to comment, however I will not react to your valuable contributions until I return from my holidays in two weeks time.
> 
> Ed
> 
> 
> On Mon, 1 Aug 2016 at 11:07 Rob Atkinson <rob@metalinkage.com.au <mailto:rob@metalinkage.com.au>> wrote:
> what - we all have funny shaped heads?  :-)
> 
> 
> 
> On Mon, 1 Aug 2016 at 19:14 Ed Parsons <eparsons@google.com <mailto:eparsons@google.com>> wrote:
> CRS are not standardised for the same reason we don't all speak English :-)  I will however give it a go..
> 
> ed
> 
> 
> On Mon, 1 Aug 2016 at 07:39 Linda van den Brink <l.vandenbrink@geonovum.nl <mailto:l.vandenbrink@geonovum.nl>> wrote:
> Hi,
> 
>  
> 
> I still remember well when I started working at Geonovum and first found out that there were many different coordinate reference systems. It seemed very silly to me that this was not standardized.
> 
>  
> 
> When one of you takes up Jeremy’s challenge, please see what is already written about CRS in http://w3c.github.io/sdw/bp/#ref-crs <http://w3c.github.io/sdw/bp/#ref-crs> . It makes sense to move some of this to an introductory section in the front of the document, and any content making this section more accessible is welcome!
> 
>  
> 
> Linda
> 
>  
> 
> Van: Jeremy Tandy [mailto:jeremy.tandy@gmail.com <mailto:jeremy.tandy@gmail.com>] 
> Verzonden: zaterdag 30 juli 2016 10:06
> Aan: SDW WG Public List; Ed Parsons
> Onderwerp: 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 <https://lists.w3.org/Archives/Public/public-sdw-wg/2016Jul/0336.html> 
> 
> [2]: https://epsg.io/3857 <https://epsg.io/3857> 
> 
> [3]: http://w3c.github.io/sdw/bp/#spatial-things-features-and-geometry <http://w3c.github.io/sdw/bp/#spatial-things-features-and-geometry> 
> 
> [4]: http://w3c.github.io/sdw/bp/#spatial-relations <http://w3c.github.io/sdw/bp/#spatial-relations> 
> 
> -- 
> Ed Parsons FRGS
> Geospatial Technologist, Google
> 
> Google Voice +44 (0)20 7881 4501 <tel:%2B44%20%280%2920%207881%204501>
> www.edparsons.com <http://www.edparsons.com/> @edparsons
> 
> -- 
> Ed Parsons FRGS
> Geospatial Technologist, Google
> 
> Google Voice +44 (0)20 7881 4501 <tel:%2B44%20%280%2920%207881%204501>
> www.edparsons.com <http://www.edparsons.com/> @edparsons
> 


Received on Monday, 1 August 2016 16:31:23 UTC

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