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: (01)
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. (02)
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. (03)
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
+ max & min
* Error bars for all locations (a useful concept for all measured values). (04)
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. (05)
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. (06)
== doug foxvog (07)
> 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?
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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 (09)
"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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