Geometry Boost List: Re: [geometry] Support for geographic coordinate system

Subject: Re: [geometry] Support for geographic coordinate system
From: Adam Wulkiewicz (adam.wulkiewicz_at_[hidden])
Date: 2014-11-17 19:53:05

Hi,

Barend Gehrels wrote:
> Adam Wulkiewicz wrote On 14-11-2014 12:33:
>> Since we already have bg::cs namespace, somehow related to the 
>> reference system. We could reuse this scheme:
>>
>> boost::geometry::rs::spheroid<>
>
>
> The common abbreviation is srs (spatial reference system), so as we 
> get to that direction, I would certainly use that one. That would 
> actually look quite good.
>
>
>>
>> but should spheroid and sphere be included in reference systems 
>> (namespace)? They're rather models describing the ref systems. Though 
>> it's possible that we'd need a place for more code related to 
>> reference systems, EPSGs, SRIDs, etc. so this code could be put 
>> there. But then I'd put the models in:
>>
>> boost::geometry::rs::model::sphere<>
>> boost::geometry::rs::model::spheroid<>
>>
>> Or just reuse the namespace cs for this:
>>
>> boost::geometry::cs::model::sphere<>
>> boost::geometry::cs::model::spheroid<>
>>
>> which would be probably the most general choice. The question is: 
>> could additional things be put in the bg::cs namespace?
>
>
> I think I would prefer the srs namespace.

Indeed srs is a better name than rs. Though I'm not sure that we should 
use it. On the wikipedia 
(http://en.wikipedia.org/wiki/Spatial_reference_system) there states:

A spatial reference system (SRS) or coordinate reference system (CRS) is 
a coordinate-based local, regional or global system used to locate 
geographical entities. A spatial reference system defines a specific map 
projection, as well as transformations between different spatial 
reference systems.
(...)
Spatial reference systems can be referred to using a SRID integer, 
including EPSG codes (...)

AFAIU SRS is higher-level concept than sphere and spheroid models 
representing a coordinate system. By using those models I'm not defining 
any particular SRS since AFAIR SRS should also define other things like 
units and the N/S W/E mapping, etc. The concept of SRS is bound closely 
with geography/GIS and on this level I'd prefer to be domain-agnostic, 
in other words be closer to mathematics. Newly added sphere/spheroid 
represent a global system, not necesarily for geographical entities.

Does the above have some sense?

Regards,
Adam