Doug and Sean, (01)
The reason for the variation of Berlin's position according to Sean's
sources is not so much the extent of the urban area. It's rather due to
a bad choice of coordinates by the NY Times. If you look up the position
that it specifies, you end up near a small village north of Berlin. (02)
On 27/10/2010 06:40, doug foxvog wrote:
> On Tue, October 26, 2010 14:49, sean barker said:
>> Just to add to the problem, it is interesting to compare the position of
>> Berlin according to various sources:
> Berlin is almost 900 sq. km. Giving its position to centi-microns, as
> Geonames does makes no sense. If there is a an official marker from
> which distances are measured, it makes some sense to give its location
> to the closest meter. Specifying its center to the decimeter is not
> very useful.
> An ontology for representing static places that extend in area needs more
> than just to specify a single point. There are different ways to do this.
> Useful concepts to include in an ontology are
> * defined reference location
> * boundary curve(s) as one or more sets of vertexes with straight lines
> (or arcs) connecting them
> * bounding and bounded Mercator rectangle
> * bounding/bounded circle
> * Elevation
> + average
> + max& min
> * Error bars for all locations (a useful concept for all measured values).
> Just like other measured values, the ontology should have multiple units
> (and in this case systems of units) in which positions can be expressed.
> Conversion tools or services should allow a value to be input/output
> using any appropriate desired system.
> Moving objects would have a relation that specifies their 2D or 3D location
> at given times. Tools could generate 4D locations as needed from 3+1D.
> == doug foxvog
>> Displayed as N52 31'27", E13 24'37", and 52.52437 13.41053
>> New York Times 52.6166667, 13.4 as geo: lat, long
>> DBpedia - 52.500557, 13.398889 as geo:lat long
>> AND 52 30' 2" 13 23' 56" as dbpprop:latd, latm, lats, longd, longm,
>> Freebase 52.52334 13.41269, contained by Germany, Europe
>> The positions agree within about 1 km in longitude, but in longitude the
>> variation is of the order of 10 km.
>> Sean Barker
>> Bristol, UK
>>> -----Original Message-----
>>> From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
>>> [mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Chris
>>> Sent: 26 October 2010 12:46
>>> To: '[ontolog-forum] '
>>> Subject: Re: [ontolog-forum] Fw: GPS coordinates in an ontology?
>>> *** WARNING ***
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>>> Ian mentions below I had done some work in this area.
>>> As Sean said earlier, it is useful to distinguish between the object
>>> being represented and its representation.
>>> As Ian points out below, it can take some effort to be sure what object
>>> is being presented.
>>> The team found that it is often geo-spatial (all three dimensions) and
>>> temporal data - rather than just spatial data that is of interested (at
>>> least in the defence domain we were working in). We are often interested
>>> in the things that stay in the same place (place? See Aristotle for more
>>> details) over time.
>>> Maybe because we have a 4D bias :-) we found a 4D approach useful.
>>> I give some pointers to the 4D approach below.
>>> A geo-spatial (all three dimensions) and temporal position (point) is a
>>> point in 4D.
>>> So (as Ian says below) if we were not interested in the temporal
>>> - in programming terms, it was stripped out - then we have a point in 3D
>>> (with an associated time) and a line in 4D.
>>> If (as Ian says below) we were not interested in the altitude
>>> co-ordinate - in programming terms, it was stripped out - then we have a
>>> line in 3D (with an associated time) and 4D.
>>> There were the standard issues about whether the line was the tangent to
>>> the normal of some reference ellipsoid or through some notional centre
>>> of the earth.
>>> If we were not interested in either the altitude or temporal
>>> co-ordinates, then we have a line in 3D and a plane in 4D.
>>> Interestingly we found that taking the 4D approach revealed some
>>> potential improvements in airspace management.
>>> We were interested and amused to find the term 4DATM (4D Air Traffic
>>> Management) is in use - whereas from our perspective this follows the
>>> traditional 3D + 1 approach (i.e. it is not 4D in our sense of the
>>> Our take on this was that this recognised the importance of looking at
>>> space and time together (for things like ATM) but did not make the
>>> (paradigm?) shift from 3D + 1 to 4D.
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> doug foxvog doug@xxxxxxxxxx http://ProgressiveAustin.org
> "I speak as an American to the leaders of my own nation. The great
> initiative in this war is ours. The initiative to stop it must be ours."
> - Dr. Martin Luther King Jr.
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