[CITE-Forum] reopnened: BBOX with zero extent (was: Re: Solved)

Arnulf Christl arnulf.christl at metaspatial.net
Tue Apr 9 15:47:00 EDT 2013


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Hi,
instead I would suggest to modify the standard and add an informative
section:

1. "A Bounding Box should not have zero area."
Reasoning: A point geometry has by definition a zero extent (area),
anything else would be an arbitrary.

Then add something like this:

Informative note:
Point geometries have by definition a zero extent and software has to
make sure this does not lead to division by zero (or whatever else
tech note might help to clarify the point).

Reasoning: This will make sure that implementers look into the problem
and make sure their software handles the problem correctly by at least
producing a sensible error message.

Cheers,
Arnulf


On 04/09/2013 07:05 PM, Richard Martell wrote:
> Hi all,
> 
> 
> Clause 6.7.4 in ISO 19128 (WMS 1.3) states that:
> 
> "A Bounding Box shall not have zero area."
> 
> 
> This constraints applies to both service metadata and requests. If
> the current test suite does not verify this for the capabilities 
> document (getcapabilities.xml doesn't appear to), then a new test 
> is warranted.
> 
> 
> -- Richard
> 
> 
>> -----Original Message----- From: 
>> cite-forum-bounces+rmartell=galdosinc.com at lists.opengeospatial 
>> .org 
>> [mailto:cite-forum-bounces+rmartell=galdosinc.com at lists.openge 
>> ospatial.org] On Behalf Of Sebastian Goerke Sent: Tuesday, 02
>> April, 2013 01:02 To: cite-forum at lists.opengeospatial.org 
>> Subject: Re: [CITE-Forum] Solved
>> 
> Hi Arnulf,
> 
> the WMS spec says in 7.3.3.6 BBOX:
> 
> If a request contains an invalid BBOX (e.g. one whose minimum X is 
> greater than or equal to the maximum X, or whose minimum Y is
> greater than or equal to the maximum Y) the server shall throw a
> service exception.
> 
> This implicates, that requesting a bbox with equal ll and ur is 
> impossible for compliant WMS implementations. As a consequence,
> there is somehow an implicit requirement for WMS servers, not to
> advertise such bounding boxes as they are not useable. Maybe this
> is something for a change request.
> 
> Regards
> 
> Sebastian
> 
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> 

- -- 
Arnulf Christl
http://metaspatial.net
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