Re: [Geojson] PR #199: CRS

On Thu, Apr 21, 2016 at 5:22 AM, Martin Thomson
<martin.thomson@gmail.com> wrote:
> On 21 April 2016 at 16:50, Martin Daly <Martin.Daly@cadcorp.com> wrote:
>> Use, or reference, any CRS definition you want, but coordinates are still *always* lon/lat or easting/northing.
>
> Ok, I think that I understand what the parameters are now.
>
> Now I think that I'd like to understand why those particular parameters.

The reason to have the spec describe which coordinate is easting and
which is northing is that it lets people write clients that can render
(or otherwise process) the data *without* having to carry around a
lookup table of all possible CRS identifier to axis order
relationships that you might encounter.

A CRS-agnostic GeoJSON client can successfully render data to users in
a way that makes sense: render the first coordinate along a horizontal
axis and the second along a vertical axis.  Once you say that you can
only understand the axis order if you also have a database of every
possible CRS, you make lightweight web clients impractical.

Tim

>
> How is it that a projected CRS is OK and even ECEF, but only if
> easting is put before northing?  From the outside, it seems a little
> arbitrary.  What is the principle that you are attempting to preserve
> with this restriction?
>
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