[postgis-tickets] [PostGIS] #2991: ST_Transform using PROJ.4 strings

[PostGIS]

#2991: ST_Transform using PROJ.4 strings
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 Reporter:  mwtoews      |       Owner:  pramsey       
     Type:  enhancement  |      Status:  new           
 Priority:  medium       |   Milestone:  PostGIS Future
Component:  postgis      |     Version:                
 Keywords:               |  
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 The idea behind this enhancement is to directly use a PROJ.4 string to
 transform to/from, rather than looking up `proj4text` in `spatial_ref_sys`
 using a SRID.

 There are an infinite number of possible projections that can be described
 with a PROJ.4 string, such as projections centred on a particular geometry
 used to perform an equidistant spatial analysis. It could also be useful
 to fine-tune a `proj4text` before assigning it an SRID in
 `spatial_ref_sys`.

 Here are some ideas for the SQL signatures:
 {{{
 ST_Transform(geometry g, text to_proj, text from_proj) RETURNS geometry;
 ST_Transform(geometry g, text to_proj, integer from_srid DEFAULT NULL)
 RETURNS geometry;
 ST_Transform(geometry g, integer to_srid, text from_proj) RETURNS
 geometry;
 }}}
 Only the last signature would return a geometry with an SRID from
 `spatial_ref_sys`; all others would return a geometry with undefined SRID
 (0). With the second signature, if `from_srid` is NULL, then the SRID is
 obtained from the geometry, and an error is raised if it is undefined.

 Any thoughts? Do these signatures cover everything, or are there potential
 clashes?

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Ticket URL: <http://trac.osgeo.org/postgis/ticket/2991>
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