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Re: CRS best practices: Google Geocoding API [SEC=UNCLASSIFIED]

From: Ed Parsons <eparsons@google.com>
Date: Tue, 28 Mar 2017 10:19:57 +0000
Message-ID: <CAHrFjcnz0fvyhXxwFxQ7tTUq_i=+RYJkAgDTOP693txD59G=bA@mail.gmail.com>
To: Bruce Bannerman <bruce.bannerman@bom.gov.au>, Jon Blower <j.d.blower@reading.ac.uk>, "Simon.Cox@csiro.au" <Simon.Cox@csiro.au>, "jeremy.tandy@gmail.com" <jeremy.tandy@gmail.com>, "bcochrane@linz.govt.nz" <bcochrane@linz.govt.nz>, "public-sdw-wg@w3.org" <public-sdw-wg@w3.org>
Morning Bruce & Jon,

I think we have quite different perspectives on this can I ask you both to
actively contribute to the WG via the meetings
<https://www.w3.org/2015/spatial/wiki/Meetings#Teleconference_Agendas_and_minutes>,
It's important that we fully understand your position on this

Many Thanks

Ed


On Mon, 27 Mar 2017 at 21:37 Bruce Bannerman <bruce.bannerman@bom.gov.au>
wrote:

> Hi Jon,
>
> Thank you for your comments on this. They are most helpful.
>
> If anyone knows of any studies that can help us to better quantify the
> amount of spatial data available on the web, together with SRS info, I
> think that it would be enlighting for the document's audience.
>
> I do not equate published on the web with only that data published by
> Google and its peers.
>
> I am very aware of the many petabytes of spatial data available via
> National Met Services and various other government organisations that
> operate within Spatial Data Infrastructures.
>
> It would be good if this document was equally as relevant for this
> 'traditional' source of spatial data and also for SDIs to evolve over time
> to support a more semantic approach.
>
> Bruce
> ------------------------------
> *From:* Jon Blower <j.d.blower@reading.ac.uk>
> *Sent:* Monday, 27 March 2017 11:20:55 PM
> *To:* Ed Parsons; Simon.Cox@csiro.au; Bruce Bannerman;
> jeremy.tandy@gmail.com; bcochrane@linz.govt.nz; public-sdw-wg@w3.org
>
> *Subject:* Re: CRS best practices: Google Geocoding API [SEC=UNCLASSIFIED]
>
> Ed,
>
>
>
> Ø  our aim is to make aware and assist a primary audience who are not
>  Geo experts and have not added any explicit geospatial information to
> their data until now.
>
>
>
> That’s certainly one aim of the group. But it’s clear from the constant
> re-emergence of this debate (and others like it) that others in the group
> have other expectations, connected with making the Web a better place for
> geo professionals too. So we need to either accommodate those expectations
> or rule them out of scope.
>
>
>
> In case it wasn’t clear from my mail, I have no problem with talking
> about, and even recommending, WGS84 (sic) as long as the context is clear.
> But our outputs will have a varied audience (who will dip in and out of
> bits of our documents) and where possible we must avoid sweeping statements
> that cause concern in important sections of that audience. That’s all I’m
> saying, and we’re probably in violent agreement about most of it.
>
>
>
> Ø  I would argue that much of the Geo expert community data published in
> CRS other than WGS84 is largely invisible on the web not accessible behind
> opaque service interfaces
>
>
>
> That’s true in some cases, but there’s a mass of spatial data freely
> available as simple HTTP downloads. (I think what we’re exposing here is
> that we don’t have a good definition of what it means for data to be
> “published on the web”.)
>
>
>
> Ø  so the claim that the vast majority of spatial data on the web is
> WGS84 holds true..
>
>
>
> Whether this statement is true or not (I don’t think it is, but let’s
> disagree on that), there’s simply no need to make that strong a statement
> in our documents. It’s probably more accurate (and helpful) to say that
> publishing in WGS84 will help people to integrate data with mass-market web
> mapping technologies – why not stick with a statement along those lines?
>
>
>
> (By the way, WGS84 might be the de-facto “web standard” for point data,
> but for raster data the “web standard” would be Web Mercator – so that’s
> another reason not to be too strong in statements about WGS84.)
>
>
>
> Ø  In summary I would humbly suggest that this discussion is once again
> an example of the geospatial industry looking in on itself rather than
> out...
>
>
>
> That is an unhelpful assertion, and not true in my opinion. It only serves
> to irritate people who are trying to make our outputs better. There are
> plenty of people in the “geospatial industry” (whatever that is) looking
> out (isn’t membership of this group evidence of that?) and their concerns
> are valid too.
>
>
>
> Jon
>
>
>
>
>
> *Jon Blower *| CTO, Institute for Environmental Analytics
>
>
>
> Follow the IEA on Twitter @env_analytics
> <https://twitter.com/env_analytics> and on LinkedIn The Institute for
> Environmental Analytics (IEA)
> <https://www.linkedin.com/company/the-institute-for-environmental-analytics?trk=biz-companies-cymhttps://www.linkedin.com/company/the-institute-for-environmental-analytics?trk=biz-companies-cym>
>
>
>
> Philip Lyle Building, University of Reading, Whiteknights Campus, Reading
> RG6 6BX
>
> *T: *+44 (0)118 378 5213 <0118%20378%205213> *M: *+44 (0)7919 112687
> <07919%20112687>
>
> *E: *j.blower@the-iea.org *W: *www.the-iea.org
>
>
>
> *From: *Ed Parsons <eparsons@google.com>
> *Date: *Monday, 27 March 2017 11:54
> *To: *"Simon.Cox@csiro.au" <Simon.Cox@csiro.au>, Jon Blower <
> sgs02jdb@reading.ac.uk>, "bruce.bannerman@bom.gov.au" <
> bruce.bannerman@bom.gov.au>, Jeremy Tandy <jeremy.tandy@gmail.com>, "
> bcochrane@linz.govt.nz" <bcochrane@linz.govt.nz>, "public-sdw-wg@w3.org" <
> public-sdw-wg@w3.org>
> *Subject: *Re: CRS best practices: Google Geocoding API [SEC=UNCLASSIFIED]
>
>
>
> No surprise I feel strongly about this, I restate once again that our aim
> is to make aware and assist a primary audience who are not  Geo experts and
> have not added any explicit geospatial information to their data until now.
> Under what circumstances would a CRS other than WGS84 (sic) be the best
> choice ?
>
>
>
> We have of course another audience who are the Geo experts perhaps
> frustrated that the data they have shared so far has not had the impact in
> terms of usage that they might have hoped, to this community we offer
> alternatives that may make their content more accessible to the mainstream
> web - In this case publishing using alternative CRS such as WGS84 would
> amongst other things be beneficial.
>
>
>
> I would argue that much of the Geo expert community data published in CRS
> other than WGS84 is largely invisible on the web not accessible behind
> opaque service interfaces, so the claim that the vast majority of spatial
> data on the web is WGS84 holds true..
>
>
>
> In summary I would humbly suggest that this discussion is once again an
> example of the geospatial industry looking in on itself rather than out...
>
>
>
> Ed
>
>
>
>
>
>
>
>
>
> On Mon, 27 Mar 2017 at 11:10 <Simon.Cox@csiro.au> wrote:
>
> What Jon says.
>
> +1
>
>
>
> *From:* Jon Blower [mailto:j.d.blower@reading.ac.uk]
> *Sent:* Monday, 27 March, 2017 20:03
> *To:* Ed Parsons <eparsons@google.com>; Bruce Bannerman <
> bruce.bannerman@bom.gov.au>; Jeremy Tandy <jeremy.tandy@gmail.com>; Byron
> Cochrane <bcochrane@linz.govt.nz>; SDW WG Public List <
> public-sdw-wg@w3.org>
>
>
> *Subject:* Re: CRS best practices: Google Geocoding API [SEC=UNCLASSIFIED]
>
>
>
> Hi all,
>
>
>
> I think this debate shows we need to be careful about we phrase our key
> recommendations. I would agree with Bruce that the statement:
>
>
>
> *“(WGS 84) Coordinate Reference System is used in almost all cases where
> spatial data is published on the Web”*
>
>
>
> is overly strong and invites controversy unnecessarily. (How do we measure
> “almost all cases” anyway – by data storage? By data transferred? By number
> of “hits”? By number of datasets? They would all likely give different
> answers.) There are huge volumes of satellite imagery freely available on
> the web that are not published in WGS84, although equally they are not
> aimed at a typical “Google Maps” user. Then there are huge archives of
> weather, climate and astronomical data, all of which are spatial, and are
> not usually WGS84 either. Google Maps (and Bing, etc) have huge numbers of
> users/hits, but that doesn’t mean that they represent “almost all cases” of
> data *publication*.
>
>
>
> I think we’ve had this debate before, but I’d be more comfortable with
> statements like:
>
>
>
> “WGS84 is the most common CRS in mass-market spatial applications such as
> X, Y and Z. Publication of data in this CRS will make it easier to reach a
> wide audience of non-specialists, but publishers must be aware of the
> implications of doing so [for applications in which high accuracy is
> required].”
>
>
>
> It would also be helpful to point to some good references where
> non-specialist can learn about the issues surrounding CRSs (Perhaps we are
> doing that already?)
>
>
>
> We must be very careful to distinguish cases in which we are giving advice
> with a view to *widening the audience for spatial data*, and cases in
> which we are giving advice to spatial professionals who want to use the Web
> to *share data with each other*.
>
>
>
> All the best,
>
> Jon
>
>
>
>
>
>
>
> *From: *Ed Parsons <eparsons@google.com>
> *Date: *Monday, 27 March 2017 08:56
> *To: *Bruce Bannerman <bruce.bannerman@bom.gov.au>, Jeremy Tandy <
> jeremy.tandy@gmail.com>, Byron Cochrane <bcochrane@linz.govt.nz>, SDW WG
> Public List <public-sdw-wg@w3.org>
> *Subject: *Re: CRS best practices: Google Geocoding API [SEC=UNCLASSIFIED]
> *Resent-From: *<public-sdw-wg@w3.org>
> *Resent-Date: *Monday, 27 March 2017 08:57
>
>
>
> Hi Bruce,
>
>
>
> I think we are just going to disagree re the context of the document, to
> use your medical analogy we are aiming to produce the equivalent of your
> local pharmacy, not the university teaching hospital.
>
>
>
> My point re the Google products was not a flippant one, you could of
> course include BIng, OpenStreetMap, Facebook, Twitter, Flickr, Whatsap,
> Apple Maps, iMessage -the users of which all produce and consume spatial
> data represented using WGS84.  We are now clearly in the age where the
> majority of spatial data on the web is not produced by experts alone.
>
>
>
> Of course there are datasets and applications that use local projected CRS
> of the web, but compared to these consumer services I would imagine they
> represent a very small proportion... Of course I may be completely wrong
> and I'd be interested in your counter argument of this point ?
>
>
>
> Ed
>
>
>
>
>
>
>
> On Sun, 26 Mar 2017 at 23:08 Bruce Bannerman <bruce.bannerman@bom.gov.au>
> wrote:
>
> Hi Ed,
>
>
>
> Thanks for your comments.
>
>
>
> I do understand the context of this document.
>
>
>
> There are many sites with similar goals of making complex domains *
> *appear** simple, e.g. self help medical diagnosis, and do it yourself
> building renovation.
>
>
>
> Neither approach will help the user if they mis-diagnose a terminal
> illness, or remove a load bearing wall in ignorance.
>
>
>
> There is a time and a place for professional advice and we should not
> trivialise it.
>
>
>
> By all means, make the document as easy to use as possible, but do not
> trivialise these types of spatial issues and add the appropriate warning to
> seek professional advice.
>
>
>
>
>
> Regarding your second point regarding Google Earth/Maps:
>
>    - These numbers are truely impressive. Well done to Google.
>    - However, there is a vast difference between the number of users of a
>    product, and the amount of spatial data on the web. I stand by my comments.
>
>
>
> Kind regards,
>
>
>
> Bruce
>
>
>
>
>
> *From: *Ed Parsons <eparsons@google.com>
> *Date: *Friday, 24 March 2017 at 19:08
> *To: *Bruce Bannerman <bruce.bannerman@bom.gov.au>, Jeremy Tandy <
> jeremy.tandy@gmail.com>, Byron Cochrane <bcochrane@linz.govt.nz>, SDW WG
> Public List <public-sdw-wg@w3.org>
> *Subject: *Re: CRS best practices: Google Geocoding API [SEC=UNCLASSIFIED]
>
>
>
> Hello Bruce,
>
>
>
> Thanks for your comments, I will leave it to Jeremy to directly respond to
> your points, however I would restate the context of this document... It is
> aimed at non-specialist users who are looking to simply publish data about
> locations on the web, we want to avoid the exact situation you suggest that
> expert advice is needed each time to you need to  publish spatial data,
> sounds like we need to further simplify and clarify...
>
>
>
> One billion users of Google Maps and another billion users of Google Earth
> would I suggest indicate that  WGS84 is the most used CRS ?
>
>
>
> Ed
>
>
>
>
>
> On Fri, 24 Mar 2017 at 06:10 Bruce Bannerman <bruce.bannerman@bom.gov.au>
> wrote:
>
> Hi Jeremy,
>
>
>
> I was going to let this pass by to the keeper, having raised it many times
> before (and not wanting to join your BBQ  ;-)  ).
>
>
>
> I am slowly working through the latest Best Practice as I get time. The BP
> has come a long way and there is certainly some good work it it.
>
>
>
>
>
> However, I’m very uncomfortable with aspects of the current approach in
> the Best Practice regarding CRS and SRS in particular.
>
>
>
> Some comments:
>
>
>
>    - First para: *"you can express a location to within a few metres”*.
>    This statement ignores issues of precision and accuracy [1]. You can be as
>    precise as you like, but that does not make your data accurate. In relation
>    to the quoted text from the first paragraph, a precise coordinate
>    that purports to be within a few meters due to it’s coordinate precision
>    may in fact be inaccurate and perhaps kilometres away from that location.
>
>
>    - Second para: There is more to a SRS that a way of defining a set of
>    coordinates. We need to cover the mathematical representation of the area
>    covered by the SRS (the ellipsoid), the choice of projection to represent
>    ellipsoidal data within a two dimensional space, together with the
>    compromises that this brings to the data in representation of area, shape,
>    distance, bearing, scale, direction, etc.
>
>
>    - I note the statement *“(**WGS 84) Coordinate Reference System is
>    used in almost all **cases where spatial data is published on the Web”*.
>    I find this statement dangerous and very difficult to believe!  Can the
>    author of the statement please cite the relevant studies that support this
>    claim?
>
>
>    - There may be serious implications for either using an incorrect SRS,
>    or assuming an incorrect SRS.   Spatial data is typically used to underpin
>    a wide range of decision making activities. Some of these decisions may
>    have significant consequences to people, property and life. As an example
>    of some of the potential impact of incorrectly combining data after
>    ignoring SRS issues, please see some example diagrams referred to below:
>
>
>    - [2] image to illustrate differences in Australian SRS (ellipsoids
>       and datums) - GDA94 and AGD66
>       - [3] image to illustrate differences in SRS (projections) -
>       Lambert Conformal Conic and UTM MGA Zone 50
>       - [4] image to illustrate differences in SRS (projections) -
>       Lambert Conformal Conic and VicGrid94
>       - [5] image to illustrate differences in SRS (ellipsoids, datum and
>       projections) - Lambert Conformal Conic and World Mercator
>
>
>    - As you will see from the diagrams, if someone is combining data from
>    different SRS, without accounting for the differences between those SRS,
>    then the results of an analysis in support of a decision making process,
>    together with that decision may well be flawed with potential consequences.
>
>
>    - Spatial professionals undertake substantial tertiary study and on
>    the job work experience in order to understand their profession. We cannot
>    expect that any lay person will be able to just pick it up e.g. By .reading
>    this BP.
>
>
>    - I suggest that a valuable piece of advice for the BP is to advise
>    readers to understand that there may be a limit to their understanding of
>    specific issues and to seek professional advice where appropriate. SRS may
>    be one such issue.
>
>
>    - I may have more comments on CRS and the BP, provided that I can get
>    suitable time to continue my review.
>
>
>
> Keep up the good work on this.
>
>
>
> Kind regards,
>
>
>
> Bruce
>
>
>
>
>
> [1]
> http://2.bp.blogspot.com/-s6ypcjPzxF0/UyaU9mOg6-I/AAAAAAAAAxs/MEU1FcozbZ0/s1600/accuracy+vs+precision.jpg
>
>
>
> [2] https://wiswiki.wmo.int/tiki-download_file.php?fileId=3465
>
>
>
> [3] https://wiswiki.wmo.int/tiki-download_file.php?fileId=3467
>
>
>
> [4] https://wiswiki.wmo.int/tiki-download_file.php?fileId=3468
>
>
>
> [5] https://wiswiki.wmo.int/tiki-download_file.php?fileId=3466
>
>
>
>
>
>
>
>
>
> *From: *Jeremy Tandy <jeremy.tandy@gmail.com>
> *Date: *Wednesday, 8 March 2017 at 04:40
> *To: *Byron Cochrane <bcochrane@linz.govt.nz>, SDW WG Public List <
> public-sdw-wg@w3.org>
> *Subject: *Re: CRS best practices: Google Geocoding API
> *Resent-From: *<public-sdw-wg@w3.org>
> *Resent-Date: *Wednesday, 8 March 2017 at 04:41
>
>
>
> Hi Byron. Thanks for this feedback. I completely agree :)
>
>
>
> Hopefully BP17 [1] is clear on this now - see the note at the top of the
> "Possible Approach" section.
>
>
>
> Jeremy
>
>
>
> [1]: http://w3c.github.io/sdw/bp/#bp-crs
>
> On Tue, 7 Mar 2017 at 00:31 Byron Cochrane <bcochrane@linz.govt.nz> wrote:
>
> A BBQ! I got to get in on this . . .
>
>
>
> First off, I feel a bit uncomfortable to say “then [it's safe to] assume”
> .  Because it often isn’t as I think is Bart’s point.  Something more along
> the line of “best guess is” is better.  Then emphasize that best practice
> is that CRS with lat/long (or coordinate) order and units of measurement
> needs to be clearly stated.
>
>
>
> I want to second everything Josh stated.  I would hope that the point of
> Best Practices is to raise the bar (within reasonable  limits) and not
> stamp current common practice as best practice.  The fact that most current
> web developers only care about lat/long does not mean this is right and
> best.  It is in IMHO the main issue, in this BP, that needs to be
> addressed.  Part of the problem is that most of the general public,
> including developers, have popularly come to view the 2D Mercator view of
> the world as true when in fact it is a hugely distorted one.  Some basic
> knowledge about CRS is advantageous to data providers and web developers in
> order to encourage better use of spatial data.
>
>
>
> This is not at all to say that only geo professionals are qualified to use
> spatial data.  Basic knowledge is within reach of anyone.  I hope we
> provide some in the SDWBP.  If we also provide pointers as to where to
> learn more, all the better.  This leads to more capable developers being
> able to create more useful and user friendly products.  There are always
> tradeoffs when selecting a CRS.  That is the basic message I wish to convey
> to the more general developers, even if we only do that in a cursory way.
>
>
>
> Cheers,
>
> Byron
>
>
>
>
>
> *From:* Jeremy Tandy [mailto:jeremy.tandy@gmail.com]
> *Sent:* Saturday, 4 March 2017 6:19 a.m.
> *To:* Bart van Leeuwen
> *Cc:* Ed Parsons; SDW WG Public List
>
>
> *Subject:* Re: CRS best practices: Google Geocoding API
>
>
>
> 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
>
> *Error! Filename not specified.*
> twitter: @semanticfire
> tel. +31(0)6-53182997 <+31%206%2053182997>
> Netage B.V.
> http://netage.nl
> Esdoornstraat 3
> 3461ER Linschoten
> The Netherlands
> *Error! Filename not specified.*
>
>
>
> 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> 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> wrote:
> Hmmm.
>
> 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> 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 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> wrote:
> Hi Ed- in the introduc
>
> --


*Ed Parsons *FRGS
Geospatial Technologist, Google

+44 7825 382263 @edparsons
www.edparsons.com
Received on Tuesday, 28 March 2017 10:20:45 UTC

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