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Subject: [ggl] extensions
From: Barend Gehrels (Barend.Gehrels)
Date: 2009-10-09 08:35:11

Hi Hartmut,

Hartmut Kaiser wrote:
>> As a follow-up on the extension discussion.
>> Do you see the following things as part of the GIS extension?
>> - the latlong point (a geometry)
> What's the difference to a 'normal' point?
- it is in the 'geographic' coordinate system -> automatically the right
strategies are chosen (distance over the earth)
- it has special constructors to assign it in either latitude /
longitude or in longitude / latitude (to have less confusion but, as it
appears, it might enlarge confusions as well...)

>> - the ggl::dms parsing utility (parses a string as "52N 4E" to a
>> coordinate)
>> - the epsg coordinate system tag
>> - the geographic coordinate system
> All three should be part of the coordinate transformation extension, IMHO.
For EPSG I (maybe) agree, it exists because we have the projections

The geographic coordinate system itself does never need to be
transformed of whatsoever, you can have GPS points (in latlong, so in
this coordinaet system) and calculate distances between them (over the
earth), simplify them, etc. So I would keep this separate. It existed
long before projections.

The dms-parsing utility is also not part of transformations only, ASCII
files having these kind of coordinates can be assigned to point's
automatically. It also existed before projections were there
Regards, Barend

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