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RE: BP8: Note about axis order in WKT

From: <andrea.perego@ec.europa.eu>
Date: Wed, 3 May 2017 17:57:31 +0000
To: <public-sdw-wg@w3.org>
CC: <jeremy.tandy@gmail.com>, <l.vandenbrink@geonovum.nl>
Message-ID: <EDFF15E839F79242AA55B1468C63DDA901EB6A0E@S-DC-ESTG02-J.net1.cec.eu.int>
Dear all,

The note about axis order in WKT is now included in the ED (thanks, Linda):

http://w3c.github.io/sdw/bp/#bp-crs

It's the last note under point #3. For your convenience, I include it below:

[[
It is worth noting that, in the [SIMPLE-FEATURES] definition of WKT, the coordinate axis-order is by default longitude / latitude, irrespective of the coordinate reference system used. The same applies to EWKT (Extended WKT) - a PostGIS extension to WKT supported also by other GIS tools -, which includes a parameter (SRID) for specifying the coordinate reference system.

For this reason, whenever using WKT to encode geometries, it is important that the reference WKT specification can be unambiguously determined.
]]

Could you please have a check, and verify whether you think it's correct / accurate enough? If this is not the case, please propose revised text.

In particular, I would like to ask your feedback on the last sentence:

[[
For this reason, whenever using WKT to encode geometries, it is important that the reference WKT specification can be unambiguously determined.
]]

Ideally, this text needs to be extended to provide guidance on how to make it unambiguous which is the WKT "flavour" used. When using RDF + GeoSPARQL's WKT, datatype geosparql:wktLiteral does the job. But what about other WKT flavours? And what to do when not using an RDF representation?

Thanks In advance

Andrea

----
Andrea Perego, Ph.D.
Scientific / Technical Project Officer
European Commission DG JRC
Directorate B - Growth and Innovation
Unit B6 - Digital Economy
Via E. Fermi, 2749 - TP 262
21027 Ispra VA, Italy

https://ec.europa.eu/jrc/

----
The views expressed are purely those of the writer and may
not in any circumstances be regarded as stating an official
position of the European Commission.


________________________________________
From: PEREGO Andrea (JRC-ISPRA)
Sent: 01 May 2017 00:08
To: Jeremy Tandy; Linda van den Brink
Cc: SDW WG Public List
Subject: BP8: Note about axis order in WKT

Jeremy, Linda,

As agreed, I've prepared a draft note for BP8 about how axis order is used in (the different flavours of) WKT.

The relevant pull request (including also a number of editorial changes mainly on Section 12.2.1 and Appendix A):

https://github.com/w3c/sdw/pull/769

Thanks

Andrea

----
Andrea Perego, Ph.D.
Scientific / Technical Project Officer
European Commission DG JRC
Directorate B - Growth and Innovation
Unit B6 - Digital Economy
Via E. Fermi, 2749 - TP 262
21027 Ispra VA, Italy

https://ec.europa.eu/jrc/

----
The views expressed are purely those of the writer and may
not in any circumstances be regarded as stating an official
position of the European Commission.
Received on Wednesday, 3 May 2017 17:58:04 UTC

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