Re: [Geojson] PR #199: CRS

I was mainly thinking of the discussion in these threads

http://lists.geojson.org/pipermail/geojson-geojson.org/2013-June/000790.html <http://lists.geojson.org/pipermail/geojson-geojson.org/2013-June/000790.html>

http://lists.geojson.org/pipermail/geojson-geojson.org/2013-December/000880.html <http://lists.geojson.org/pipermail/geojson-geojson.org/2013-December/000880.html>

https://github.com/geojson/draft-geojson/pull/15 <https://github.com/geojson/draft-geojson/pull/15>

Martin Daly, Howard Butler and I were generally on the side of keeping CRS. As I said earlier, if I’m the lone holdout, I’m not going to stand in the way of closing this issue.

	Allan

> On Apr 22, 2016, at 7:54 PM, <Simon.Cox@csiro.au> <Simon.Cox@csiro.au> wrote:
> 
> Have been following this conversation with great interest. Sean's description of the situation seems very accurate to me. 
> 
> The influence of Geojson is not limited to strictly conforming applications. For example I used the GeoJSON geometry formulation within a JSON implementation of O&M published through OGC last year, but did not claim that OM-JSON was therefore GeoJSON, because it otherwise wasn't. Other elaborations and extensions and deviations will be created, including the ones Sean describes that use other crs. Under the regime proposed none of these are GeoJSON, but they are still useful, and it is better to tweak something that works than start again. 
> 
> This all seems like a very useful direction, furthermore would cease offending the precious petals in the community that care so much about crs, and thus diminish the total level of conflict in the world just a little bit. 😉
> 
> Simon
> 
> From: GeoJSON <geojson-bounces@ietf.org> on behalf of Sean Gillies <sean.gillies@gmail.com>
> Sent: Friday, 22 April 2016 10:38:41 PM
> To: Martin Daly
> Cc: Martin Thomson; geojson@ietf.org
> Subject: Re: [Geojson] PR #199: CRS
>  
> On Thu, Apr 21, 2016 at 12:50 AM, Martin Daly <Martin.Daly@cadcorp.com <mailto:Martin.Daly@cadcorp.com>> wrote:
> ...
> 
> Interoperability when using different CRSs is possible, just less likely with the wider population of GeoJSON consumers.
> 
> We discussed the possibility of banning other CRSs, but there was no consensus (quite the opposite, I think). I doubt that that has changed.
> 
> Martin,
> 
> Interoperability when using different CRS is hardly possible for GeoJSON because we don't specify a way to identify the intended CRS. If I serve you a file with coordinates like
> 
>     [4200.0, 4200.0] ...
> 
> with no other information, how are you going to use this data? There's no interoperability here.
> 
> My reading of https://github.com/geojson/draft-geojson/pull/39 <https://github.com/geojson/draft-geojson/pull/39> and other issues is that support for "other CRS are allowed but NOT RECOMMENDED" was actually lukewarm at best. Tim, Howard, and I preferred to drop CRS, along with Raj Singh. Allan originally did and then switched. I don't think consensus is settled here at all and that it is okay to revisit the question.
> 
> In https://github.com/geojson/draft-geojson/pull/6 <https://github.com/geojson/draft-geojson/pull/6> it was clear that folks who were serving projected GeoJSON were doing so without any CRS definition at all, within their own tightly coupled client-server systems (web map front ends dedicated to a particular database). Their interoperability needs: zero. The impact on their work from a change to "other CRS NOT ALLOWED": zero. As I've written elsewhere, I'm doing the same thing in production at work and am perfectly content with my representations being only GeoJSON-like, not actual standard GeoJSON.
> 
> What I'm not content with is receiving application/geo+json GeoJSON from others that uses arbitrary and unidentified coordinate reference systems.
> 
> Changing SHOULD NOT to "GeoJSON documents MUST NOT use a coordinate reference system other than the one defined here" (https://github.com/geojson/draft-geojson/pull/197#issuecomment-212898200 <https://github.com/geojson/draft-geojson/pull/197#issuecomment-212898200>) is my strong preference. If we can't do this, we should consider writing http://geojson.org/geojson-spec.html#coordinate-reference-system-objects <http://geojson.org/geojson-spec.html#coordinate-reference-system-objects> into the draft or writing a replacement for it.
> 
> -- 
> Sean Gillies
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