[postgis-devel] [PostGIS] #1331: [raster] Physically relevant geotransform settings

[PostGIS]

#1331: [raster] Physically relevant geotransform settings
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 Reporter:  bnordgren       |       Owner:  pracine              
     Type:  enhancement     |      Status:  new                  
 Priority:  medium          |   Milestone:  PostGIS Raster Future
Component:  postgis raster  |     Version:  1.5.X                
 Keywords:                  |  
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 I only have the forward calculations worked out and described on the wiki.
 I have an approach in mind for the reverse calculations.

 Algorithm documentation: DevWikiAffineParameters

 This could stand to be reviewed/edited (for clarity and correctness) by
 someone other than me. Code will follow feedback on the proposed
 algorithm.

 This approach allows users to specify the geotransform in terms of the
 following parameters:

  * The magnitude of the '''i,,b,,''' basis vector (distance between pixels
 along i axis)
  * The magnitude of the '''j,,b,,''' basis vector (distance between pixels
 along j axis)
  * The angle θ,,i,, (the angle by which the raster's grid needs to be
 rotated, positive clockwise -- for compatibility with "heading/bearing")
  * The angle θ,,ij,, (the angle from the i basis vector to the j basis
 vector positive counterclockwise -- for consistency with right-handed
 coordinate system)
  * The offsets t,,x,, and t,,y,,

 This would likely result in a single function with a signature like:

 {{{
 ST_SetGeoTransform(raster raster,
                    float8 i_magnitude,
                    float8 j_magnitude,
                    float8 theta_i default 0,
                    float8 theta_ij default -90)
 }}}

 ... or the equivalent if I pooched the SQL syntax.

 We should also downplay the scale/skew accessors after this is
 implemented. They're still relevant for copying individual parameters from
 an external source, but it's almost never appropriate to change just one
 or two of them. ...and the names for the parameters are somewhat
 misleading.

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/1331>
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