Geometry Boost List: Re: [geometry] a ring concept implementation of a true circle?

Subject: Re: [geometry] a ring concept implementation of a true circle?
From: Mats Taraldsvik (mats.taraldsvik_at_[hidden])
Date: 2012-08-29 05:01:35

Hi Bruno and Barend,

On 08/28/2012 10:49 PM, Barend Gehrels wrote:
> On 28-8-2012 18:54, Mats Taraldsvik wrote:
>> On 08/28/2012 03:47 PM, joe_at_[hidden] wrote:
>>> Is there an easy way to model a true circle? By that I mean not a 
>>> polygon with a bunch of closely spaced points, but something you 
>>> construct with a point and a radius.
>>>
>>> I guess not? All rings must consist of a list of points?
>>
>> It is not part of the simple geometry feature set, which, as far as I 
>> can see, is the only implemented data types thus far. However, the 
>> SQL-MM standard has a CIRCULARSTRING type (see 
>> http://postgis.org/docs/using_postgis_dbmanagement.html#SQL_MM_Part3). It 
>> is currently missing(?) from Boost.Geometry (but might be in future 
>> plans? Barend?)
>
> Yes, plans are there: as Bruno answered (2 minutes before your mail 
> ;-) ) we started the nsphere geometry and concepts, but they are never 
> released, so still in extensions. See Bruno's mail.
>
Ah, I see. Great! :) Does this nsphere implement (parts of) the SQL-MM 
standard? Is the resulting WRT output compatible with PostGIS?

Will both circular and straight linestrings/segments in e.g. a Ring be 
possible in the future? (Since there is no hierarchy in the geometries 
(only ranges of points) I guess this is difficult at present, but 
perhaps something to consider for the future?)

> Regards, Barend
>

Mats

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