Re: Scaling/size of geographical entities

Holger -

I know that you have an immediate issue to solve, but . . .

The following is provided as input - not a solution

As an FYI, the OASIS Emergency Management TC had a lengthy discussion about
how to handle a circle in their CAP and EDXL standards. The final decision
was a major compromise for version 1.0 of CAP. They wanted a really simple
expression of a circle by center point and radius. However, given the
limitations of this approach, the next version of CAP will provide the 
ability to
use GML to express geometry, including circles.

And this issue is huge for the location services infrastructure providers.
In the latter case, they do not use circles for exactly the reason Ron
points out. When using a Lat/Long CRS, circles become ellipses when
displayed or even more interesting shapes as one approaches the poles.

Then there are issues related to units of measure. Is the radius in
kilometers, miles, feet? This is why Ron's example show the use of uom
(Units of Measure). Dealing with the use and display of lat/long coordinates
can be so problematic, Federal agencies such as the EPA have developed
internal standards for dealing with Lat/Long coordinates!
http://www.epa.gov/edr/flatlongbr.pdf

Why say all of this? Well, if we extend the vocabulary to other geometries
and properties for those geometries, we will immediately encounter
discussion issues whose resolution will require careful consideration as
part of the GeoRSS definition to insure unambiguous semantics.

Sorry, the Geographer/Cartographer in me is showing :-)

Regards

Carl

----- Original Message ----- 
From: "Holger Knublauch" <holger@topquadrant.com>
To: <public-xg-geo@w3.org>
Cc: <public-xg-geo@w3.org>
Sent: Sunday, July 23, 2006 6:47 PM
Subject: Re: Scaling/size of geographical entities


>
> I have added geographic modeling support to our ontology development tool 
> [1].  This uses the W3C geo namespace but can be configured to use other 
> lat/long properties as well.  In the absence of a "standard" for 
> radius-like information to determine zooming, I had to introduce an 
> optional property
>
> http://www.topbraidcomposer.org/owl/2006/07/tbcgeo.owl#zoom
>
> so that the map is moved to a suitable scaling if a user clicks on an 
> entity.
>
> This is not meant as a suggestion on how to solve this issue, but just an 
> intermediate work-around based on the Google zooming.  I hope there will 
> be a better solution in the near future.
>
> Thanks
> Holger
>
> [1] 
> http://composing-the-semantic-web.blogspot.com/2006/07/geospatial-ontologies-in-topbraid.html
>
>
> Andrew Turner wrote:
>>
>> Holger Knublauch  wrote:
>>>
>>> Thanks Joshua.  With a basic glimpse on this, I would hope that the geo
>>> ontology is extended with a geo:radius attribute: it is a low hanging
>>> fruit while having feature types is probably an overkill.  To specify
>>
>> There is a radius in GeoRSS Simple:
>>
>>  <georss:point radius="500">45.256 -110.45</georss:point>
>>
>> It was at the bottom of the "Simple" page, so maybe you missed it. :)
>> Andrew
>>
>

Received on Monday, 24 July 2006 15:45:23 UTC