Re: UCR issue: phrasing of CRS requirement(s)

Agreed..

Ed

On Fri, 29 May 2015 at 12:10 Frans Knibbe <frans.knibbe@geodan.nl> wrote:

> Hello Ed,
>
> Yes, we could recommend using the EPSG descriptions in the BP. That is
> future work. But looking ahead to that, I think the EPSG registry has
> some issues: CRS are not identified with a URI, it is hard to
> automatically process CRS data, and CRS do not have the same axis order.
> I think CRS registries like those made available by the OGC and IGN
> France are an improvement, at least in those respects.
>
> Do you agree with the proposed requirement?
>
>
> Greetings,
> Frans
>
> 2015-05-27 15:29 GMT+02:00 Ed Parsons <eparsons@google.com>:
>
>> Describing CRS attributes is a "can of worms" for is, I would rather we
>> just point to the EPSG repository for simplicity. Perhaps we could in the
>> BP point out a few well used CRS and their EPSG descriptions.
>>
>> Ed
>>
>> Ed Parsons
>> Geospatial Technologist, Google
>>
>> Mobile: +44 (0)7825 382263
>> www.edparsons.com @edparsons
>> On 27 May 2015 13:49, "Frans Knibbe" <frans.knibbe@geodan.nl> wrote:
>>
>>> Hello all,
>>>
>>> It is nice to see a good discussion with lots of outside references and
>>> proposals for meeting the requirements. But I would like to get back to the
>>> issue of phrasing the requirements.
>>>
>>> Linda was right in noting that the requirement for a default or
>>> canonical has not been listed in the UCR document yet. I will add it. It
>>> will be very interesting to see if we can succeed in finding such a CRS.
>>> But that is something that will become clear when we work on the Best
>>> Practices.
>>>
>>> As for the phrasing of the CRS requirement, I would like to propose the
>>> following:
>>>
>>> "There should be a standard for publishing data about coordinate
>>> reference systems (CRS). It should be applicable to any 2D or 3D CRS,
>>> not only geographical reference systems. CRS descriptions should be
>>> referencable by HTTP URIs."
>>>
>>> I think that given the context of this WG (spatial data on the web),
>>> the requirement that things should be referencable goes without saying,
>>> but I have made it explicit nonetheless.
>>>
>>> I should note that when put this way, there is no requirement for having
>>> a registry of CRSs - anyone can publish a CRS defintion anywhere.
>>>
>>> Would it be sensible to add some information about what kind of data we
>>> would expect when a CRS is described? There could be a need for having
>>> complete descriptions that allow automatic coordinate transformation. Or we
>>> could try to list a few CRS attributes that we consider essential for
>>> common usage (like axis order, units, whether it is spherical or flat
>>> plane, spatial coverage....)
>>>
>>> Greetings,
>>> Frans
>>>
>>>
>>> 2015-05-26 21:12 GMT+02:00 Krzysztof Janowicz <janowicz@ucsb.edu>:
>>>
>>>> Krzysztof, why is Java such a hot bed of linked data?!?
>>>>>
>>>>
>>>> Good question. If you look at the detailed map here
>>>> http://stko.geog.ucsb.edu/pictures/lstd_map.png you will see massive
>>>> data errors. Based on our 14+ million sample, it looks like about 10% of
>>>> all linked geographic data has some issues related to it. In many cases
>>>> those issues were systematic and we notified the data providers, e.g.,
>>>> DBpedia. For instance, the dense block-like areas in China are in fact
>>>> places from the US east coast. I will look into the data from Java and will
>>>> let you know if I find something interesting.
>>>>
>>>> Anyway, the systematic list of errors may turn out to be useful for our
>>>> sdw group as it illustrates what typically goes wrong.
>>>>
>>>> Best,
>>>> Krzysztof
>>>>
>>>>
>>>>
>>>>
>>>> On 05/18/2015 07:39 AM, Kerry.Taylor@csiro.au wrote:
>>>>
>>>>> WGS84 is certainly widely used for linked data in practice, probably
>>>>> heavily influenced by this http://www.w3.org/2003/01/geo/, commonly
>>>>> called "geo".
>>>>>
>>>>> Oddly, perhaps, schema.org seems not to care about CRS at all:
>>>>> http://schema.org/GeoCoordinates
>>>>>
>>>>> Can we take inspiration from the former one  (geo)  and admit
>>>>> alternative CRSs that must be identified by virtue of the ontology (and
>>>>> therefore namespace, assuming a 1-1 relationship) that is used?  We could
>>>>> perhaps develop a couple ourselves (perhaps a WGS84-like one, and another
>>>>> for a relative 3D system), and then allow any other to be used by virtue of
>>>>> reference to the intended vocabulary (as our best practice advice)?
>>>>>
>>>>> Maybe this is a cop-out but it is a way of dealing with the common
>>>>> cases blindly, yet requiring a CRS to be implicitly identified, and also
>>>>> enabling the use of more complex or niche CRS whenever needed. We won't
>>>>> stop people making mistakes, whatever we do.
>>>>>
>>>>> This could do for  *referencing* a  CRS without ever needing a
>>>>> "default". For the *description" of a CRS, I would vote to defer that to
>>>>> the OGC by its existing methods, and I see no reason why that description
>>>>> needs to have a linked data representation,  beyond an ontology that
>>>>> permits its use.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> Krzysztof, why is Java such a hot bed of linked data?!?
>>>>>
>>>>> Kerry
>>>>>
>>>>>
>>>>>  -----Original Message-----
>>>>>> From: Svensson, Lars [mailto:L.Svensson@dnb.de]
>>>>>> Sent: Monday, 18 May 2015 9:44 PM
>>>>>> To: Ed Parsons; janowicz@ucsb.edu
>>>>>> Cc: SDW WG Public List
>>>>>> Subject: RE: UCR issue: phrasing of CRS requirement(s)
>>>>>>
>>>>>> On Monday, May 18, 2015 12:24 PM, Ed Parsons wrote:
>>>>>>
>>>>>>  In most cases I don't think they actually do mean WGS84 as in the
>>>>>>> ellipsoid and datum.
>>>>>>>
>>>>>>> I would guess it is usually shorthand for the the full spatial
>>>>>>> reference system defined by EPSG4326 or more likely on the web
>>>>>>> EPSG:3857
>>>>>>>
>>>>>> My fear is that in some cases the data providers don't really know
>>>>>> what
>>>>>> their coordinates mean in terms of ellipsoid, datum and reference
>>>>>> system. They have some coordinates taken from geonames, Wikipedia or
>>>>>> some other source and haven’t really thought of that (geographic)
>>>>>> coordinates are not just coordinates but that there is a context to
>>>>>> that, too. To what extent we can assume that they mean CRS84, I don't
>>>>>> know.
>>>>>>
>>>>>> So I think I'm on the same page as Linda on this.
>>>>>>
>>>>>> Best,
>>>>>>
>>>>>> Lars
>>>>>>
>>>>>>  On 16 May 2015 at 04:02, Krzysztof Janowicz <janowicz@ucsb.edu>
>>>>>>>
>>>>>> wrote:
>>>>>>
>>>>>>> right, so how can they be sure they mean WGS84?
>>>>>>>
>>>>>>> Here is a funny example how this can go wrong and went wrong in the
>>>>>>>
>>>>>> past:
>>>>>>
>>>>>>> http://stko.geog.ucsb.edu/location_linked_data (See the Copernicus
>>>>>>> crater)
>>>>>>>
>>>>>>> Best,
>>>>>>> Krzysztof
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On 05/15/2015 04:27 AM, Peter Baumann wrote:
>>>>>>> right, so how can they be sure they mean WGS84? if I copy-past
>>>>>>> coordinates from web info about Germany then in the past this used to
>>>>>>> be Gauss-Krüger, and several strips = sub-systems. Now let's talk
>>>>>>> about height and SI vs imperial units etc - what default could we
>>>>>>>
>>>>>> agree on?
>>>>>>
>>>>>>> With a default, all coordinate info out there on the Web (flat,
>>>>>>> height/depth, time, pressure, ...) will often be interpreted wrongly.
>>>>>>> IMHO we should rather encourage, for m2m communication, that we
>>>>>>> achieve informational completeness.
>>>>>>>
>>>>>>> my 2 cents,
>>>>>>> Peter
>>>>>>>
>>>>>>> On 05/15/15 13:21, Linda van den Brink wrote:
>>>>>>> Hi all,
>>>>>>>
>>>>>>> OK, that could be the consensus within OGC, but the GeoJSON spec does
>>>>>>> describe a default CRS and I can understand this very well. Non-
>>>>>>>
>>>>>> experts, i.e.
>>>>>>
>>>>>>> people from outside the geospatial domain who are using or want to
>>>>>>>
>>>>>> use
>>>>>>
>>>>>>> geospatial data, often have no idea that there even *are* multiple
>>>>>>> coordinate reference systems.
>>>>>>>
>>>>>>> Linda
>>>>>>>
>>>>>>> Van: Peter Baumann [mailto:p.baumann@jacobs-university.de]
>>>>>>> Verzonden: vrijdag 15 mei 2015 13:01
>>>>>>> Aan: Linda van den Brink; Frans Knibbe; SDW WG (public-sdw-wg@w3.org
>>>>>>> )
>>>>>>> Onderwerp: Re: UCR issue: phrasing of CRS requirement(s)
>>>>>>>
>>>>>>> Hi all,
>>>>>>>
>>>>>>> FYI, there has been a vivid discussion in OGC on default CRSs on the
>>>>>>> occasion of JSON coming up with such an idea, and OGC very much and
>>>>>>> strongly agreed that this is not a good idea.
>>>>>>>
>>>>>>> In general, a coordinate tuple should have exactly one CRS referenced
>>>>>>> which may include
>>>>>>> - spatial horizontal (such as Lat/Long)
>>>>>>> - time (possibly using different calendars)
>>>>>>> - elevation
>>>>>>> - anything else (eg, atmospheric sciences like to use pressure as a
>>>>>>> proxy for
>>>>>>> height)
>>>>>>> - finally, planetary CRSs are more and more coming into play as well.
>>>>>>> I sense that this is very much in alignment with the ideas that we
>>>>>>>
>>>>>> are
>>>>>>
>>>>>>> discussing here.
>>>>>>>
>>>>>>> OTOH, it is indeed important to have one common mechanism of
>>>>>>> describing CRSs. As mentioned earlier, OGC has such mechanisms in
>>>>>>> place through CRS WKT plus the CRS Name Type Specification (maybe
>>>>>>> quite misleading in its title, it allows to describe CRSs by
>>>>>>>
>>>>>> composing
>>>>>>
>>>>>>> them from other ones, such as flatland
>>>>>>> + time, flatland + pressure, flatland + depth, flatland + geological
>>>>>>>
>>>>>> time).
>>>>>>
>>>>>>> So definitely supporting Linda's observation on referencing vs
>>>>>>>
>>>>>> describing.
>>>>>>
>>>>>>> -Peter
>>>>>>>
>>>>>>> On 05/15/15 09:40, Linda van den Brink wrote:
>>>>>>> Hi Frans,
>>>>>>>
>>>>>>> I noticed that a requirement related to this is in the spreadsheet
>>>>>>>
>>>>>> but
>>>>>>
>>>>>>> not (yet?) in the UCR document. It is this requirement:
>>>>>>>
>>>>>>> “There should be a default CRS that is assumed when nog CRS is
>>>>>>>
>>>>>> specified”
>>>>>>
>>>>>>> (s/nog/no)
>>>>>>>
>>>>>>> WGS84/lat lng is the de facto standard CRS for spatial data on the
>>>>>>> web. Both publishing and using spatial data on the web should be easy
>>>>>>> for non-experts, so this requirement of having a default CRS makes a
>>>>>>> lot of sense to me. The most common cases become more easy that way.
>>>>>>>
>>>>>> I think this should be added to par.
>>>>>>
>>>>>>> 5.6 of the UCR.
>>>>>>>
>>>>>>> In this light (i.e. usability for non-expert users), the best
>>>>>>>
>>>>>> practice
>>>>>>
>>>>>>> should have information about how data owners should describe, how
>>>>>>> users can recognize and what tools they can use to transform non-
>>>>>>>
>>>>>> WGS84
>>>>>>
>>>>>>> coordinate systems to the coordinate system they need.
>>>>>>>
>>>>>>> A second point I’d like to make is that CRS should be suitable also
>>>>>>> for non- geographical reference systems (for non-Earth oriented
>>>>>>> applications).I think this is covered by 5.14, but the text of that
>>>>>>> paragraph is not completely clear to me. )“Standards for spatial data
>>>>>>> on the web should be independent on the reference systems that are
>>>>>>> used for data.”)
>>>>>>>
>>>>>>> Finally, to answer the question in the issue, as I read it, req A is
>>>>>>> not replaceable by req B. Req A is about *referencing* a CRS, while
>>>>>>> req B is about *describing* a CRS – i.e. the description you get
>>>>>>>
>>>>>> about
>>>>>>
>>>>>>> the CRS when you dereference  a CRS reference.
>>>>>>>
>>>>>>> Linda
>>>>>>>
>>>>>>> Van: Frans Knibbe [mailto:frans.knibbe@geodan.nl]
>>>>>>> Verzonden: woensdag 13 mei 2015 14:20
>>>>>>> Aan: SDW WG Public List
>>>>>>> Onderwerp: UCR issue: phrasing of CRS requirement(s)
>>>>>>>
>>>>>>> Hello all,
>>>>>>>
>>>>>>> I have raised an issue for the UCR document: ISSUE-10.
>>>>>>> All help in getting this issue resolved is very welcome.
>>>>>>>
>>>>>>> Regards,
>>>>>>> Frans
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> Frans Knibbe
>>>>>>> Geodan
>>>>>>> President Kennedylaan 1
>>>>>>> 1079 MB Amsterdam (NL)
>>>>>>>
>>>>>>> T +31 (0)20 - 5711 347
>>>>>>> E frans.knibbe@geodan.nl
>>>>>>> www.geodan.nl
>>>>>>> disclaimer
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> Dr. Peter Baumann
>>>>>>>   - Professor of Computer Science, Jacobs University Bremen
>>>>>>>     www.faculty.jacobs-university.de/pbaumann
>>>>>>>     mail: p.baumann@jacobs-university.de
>>>>>>>     tel: +49-421-200-3178, fax: +49-421-200-493178
>>>>>>>   - Executive Director, rasdaman GmbH Bremen (HRB 26793)
>>>>>>>     www.rasdaman.com, mail: baumann@rasdaman.com
>>>>>>>     tel: 0800-rasdaman, fax: 0800-rasdafax, mobile: +49-173-5837882
>>>>>>>
>>>>>> "Si
>>>>>>
>>>>>>> forte in alienas manus oberraverit hec peregrina epistola incertis
>>>>>>> ventis dimissa, sed Deo commendata, precamur ut ei reddatur cui soli
>>>>>>> destinata, nec preripiat quisquam non sibi parata." (mail disclaimer,
>>>>>>> AD 1083)
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> Dr. Peter Baumann
>>>>>>>   - Professor of Computer Science, Jacobs University Bremen
>>>>>>>     www.faculty.jacobs-university.de/pbaumann
>>>>>>>     mail: p.baumann@jacobs-university.de
>>>>>>>     tel: +49-421-200-3178, fax: +49-421-200-493178
>>>>>>>   - Executive Director, rasdaman GmbH Bremen (HRB 26793)
>>>>>>>     www.rasdaman.com, mail: baumann@rasdaman.com
>>>>>>>     tel: 0800-rasdaman, fax: 0800-rasdafax, mobile: +49-173-5837882
>>>>>>>
>>>>>> "Si
>>>>>>
>>>>>>> forte in alienas manus oberraverit hec peregrina epistola incertis
>>>>>>> ventis dimissa, sed Deo commendata, precamur ut ei reddatur cui soli
>>>>>>> destinata, nec preripiat quisquam non sibi parata." (mail disclaimer,
>>>>>>> AD 1083)
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> Krzysztof Janowicz
>>>>>>>
>>>>>>> Geography Department, University of California, Santa Barbara
>>>>>>> 4830 Ellison Hall, Santa Barbara, CA 93106-4060
>>>>>>>
>>>>>>> Email: jano@geog.ucsb.edu
>>>>>>> Webpage: http://geog.ucsb.edu/~jano/
>>>>>>> Semantic Web Journal: http://www.semantic-web-journal.net
>>>>>>>
>>>>>>
>>>>
>>>> --
>>>> Krzysztof Janowicz
>>>>
>>>> Geography Department, University of California, Santa Barbara
>>>> 4830 Ellison Hall, Santa Barbara, CA 93106-4060
>>>>
>>>> Email: jano@geog.ucsb.edu
>>>> Webpage: http://geog.ucsb.edu/~jano/
>>>> Semantic Web Journal: http://www.semantic-web-journal.net
>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> Frans Knibbe
>>> Geodan
>>> President Kennedylaan 1
>>> 1079 MB Amsterdam (NL)
>>>
>>> T +31 (0)20 - 5711 347
>>> E frans.knibbe@geodan.nl
>>> www.geodan.nl
>>> disclaimer <http://www.geodan.nl/disclaimer>
>>>
>>>
>
>
> --
> Frans Knibbe
> Geodan
> President Kennedylaan 1
> 1079 MB Amsterdam (NL)
>
> T +31 (0)20 - 5711 347
> E frans.knibbe@geodan.nl
> www.geodan.nl
> disclaimer <http://www.geodan.nl/disclaimer>
>
>  --

Ed Parsons
Geospatial Technologist, Google

Mobile +44 (0)7825 382263
www.edparsons.com @edparsons