W3C home > Mailing lists > Public > public-sdw-wg@w3.org > March 2017

Re: CRS best practices: Google Geocoding API

From: Jeremy Tandy <jeremy.tandy@gmail.com>
Date: Fri, 03 Mar 2017 17:18:39 +0000
Message-ID: <CADtUq_0rDp_WzO1XRAjH+--i1gxyw0N9bVi-e3cACHeJPiXDHA@mail.gmail.com>
To: Bart van Leeuwen <bart_van_leeuwen@netage.nl>
Cc: Ed Parsons <eparsons@google.com>, SDW WG Public List <public-sdw-wg@w3.org>
To be fair, the Google Geocoding API (which was where I started) uses
latitude and longitude - so at least it's obvious that the coordinate
position is some form angular measurement for anywhere on the Earth.


Jeremy
On Fri, 3 Mar 2017 at 17:14, Bart van Leeuwen <bart_van_leeuwen@netage.nl>
wrote:

> The problem with this definition is that the term "world view" is rather
> ambiguous.
> I know a lot of Dutch public servants in geospatial related fields who's
> world view is no bigger then the 300x300km dutch CRS.
> They assume the RD CRS as their "world view" making all wgs84 ( especially
> the negative numbers ) utterly confusing.
>
> As much as I understand that the 'world view' of web developers is WGS84
> assuming it for our audience might actually turn up the heat :)
>
> My 2 cents.
>
> Met Vriendelijke Groet / With Kind Regards
> Bart van Leeuwen
>
>
> twitter: @semanticfire
> tel. +31(0)6-53182997
> Netage B.V.
> http://netage.nl
> Esdoornstraat 3
> 3461ER Linschoten
> The Netherlands
>
>
>
>
> From:        Jeremy Tandy <jeremy.tandy@gmail.com>
> To:        Ed Parsons <eparsons@google.com>, SDW WG Public List <
> public-sdw-wg@w3.org>
> Date:        03-03-2017 17:22
> Subject:        Re: CRS best practices: Google Geocoding API
> ------------------------------
>
>
>
> Fair enough.
>
> I suppose that if we write stuff in the BP document like this, we're
> documenting what is actually happening.
>
> There's a risk that we end up encouraging people to be lazy and not bother
> to think about CRS. But then, if they're in the <*rest of the world view
> "that I just need to use Lat & Long - Period :-)"*>TM then they will
> probably not even have considered that this is an issue in the first place.
> At least this advice is consistent with geospatial data collected from the
> vast majority of [consumer] devices on the planet - because they're using
> GPS.
>
> Jeremy
>
> On Fri, 3 Mar 2017 at 16:16 Ed Parsons <*eparsons@google.com*
> <eparsons@google.com>> wrote:
> I think the first part is OK, the vertical datum part is less common and
> as a result it's more difficult to make a similar assumption.
>
> Ed
>
>
> On Fri, 3 Mar 2017 at 16:11 Jeremy Tandy <*jeremy.tandy@gmail.com*
> <jeremy.tandy@gmail.com>> wrote:
> Hmmm.
>
> *schema.org* <http://schema.org/> documents go to the trouble of saying
> "WGS 84" (although they don't describe the units either).
>
> So (as much as most of the Geo-establishment will flame me for it) should
> we be saying:
>
> "If neither your data nor the specification to which your data conforms to
> defines the coordinate reference system used, then [it's safe to] assume
> that the data with coordinate pairs uses longitude and latitude, defined in
> decimal degrees, and data with coordinate positions that have three values
> is longitude, latitude and elevation, defined in decimal degrees, decimal
> degrees and meters above sea-level. In both cases, the WGS 84 [geodetic]
> datum is assumed."
>
> Let the barbecue begin.
>
> Jeremy
>
>
> On Fri, 3 Mar 2017 at 16:02 Ed Parsons <*eparsons@google.com*
> <eparsons@google.com>> wrote:
> I think you are experiencing the rest of the world view "that I just need
> to use Lat & Long - Period :-)"
>
> The use of WGS84 is documented here
> *https://developers.google.com/maps/documentation/javascript/maptypes*
> <https://developers.google.com/maps/documentation/javascript/maptypes> if
> you go looking for it, must I would argue that most mainstream web
> developers don't need to know..
>
> btw this is also quite a nice explanation of tile based spatial indices ;-)
>
> Ed
>
>
>
> On Fri, 3 Mar 2017 at 15:14 Jeremy Tandy <*jeremy.tandy@gmail.com*
> <jeremy.tandy@gmail.com>> wrote:
> Hi Ed- in the introductory material you wrote about CRS you make a
> reference to the Google Geocoding API [1], in that its responses explicitly
> state Lat and Long rather than a coordinate pair of ambiguous order.
>
> Lat and Long are, by definition, angular measurements. OK - got that.
>
> But parsing through the API documentation, I can't see any reference to
> the units or datum which is used.
>
> Being a human, I'm prepared to guess that these are decimal degrees
> (because they look like floating point numbers). Easy for machines to
> figure that out too.
>
> As a human, I'm also prepared to guess that the API uses the WGS84. But
> that is a tricky leap for machines to work out.
>
> Does the API documentation say "WGS84" anywhere? If so, can you point me
> to it so I can refer to this explicitly? And if not, can you either justify
> why it doesn't matter, or get your colleagues to update the documentation
> (and then send me a link!).
>
> (I think that we've all agreed that it's dangerous to _assume_ a CRS :-) )
>
> Thanks, Jeremy
>
> [1]: *https://developers.google.com/maps/documentation/geocoding/intro*
> <https://developers.google.com/maps/documentation/geocoding/intro>
> --
>
> *Ed Parsons *FRGS
> Geospatial Technologist, Google
>
> Google Voice *+44 (0)20 7881 4501* <%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* <%2B44%20%280%2920%207881%204501>
> *www.edparsons.com* <http://www.edparsons.com/> @edparsons
>
>


picture
(image/jpeg attachment: 01-part)

picture
(image/jpeg attachment: 02-part)

picture
(image/jpeg attachment: 03-part)

Received on Friday, 3 March 2017 17:42:43 UTC

This archive was generated by hypermail 2.3.1 : Friday, 3 March 2017 17:42:43 UTC