[postgis-devel] [PostGIS] #1353: [raster] ST_SetRotation incorrect

PostGIS trac at osgeo.org
Wed Feb 8 06:55:30 PST 2012

#1353: [raster] ST_SetRotation incorrect
 Reporter:  bnordgren  |       Owner:  dzwarg               
     Type:  defect     |      Status:  new                  
 Priority:  high       |   Milestone:  PostGIS Raster Future
Component:  raster     |     Version:  trunk                
 Keywords:             |  
Changes (by bnordgren):

  * type:  enhancement => defect


 Replying to [comment:2 dzwarg]:
 > The initial implementation of ST_SetRotation does not preserve the angle
 between the basis vectors by design. This is a future enhancement.


 Is there any reference to this design? If it's not rotating the entire
 plane around the origin, what is it doing?

 Whatever it's intending to do, it is ''always'' an error to leave the
 raster with both i and j pointing in the same direction (or opposite
 directions). This happens even in your own test case, as indicated above.
 If you intend to defer preserving the angle between basis vectors until
 some future date, this artifact needs to be fixed now. But I can't help
 you with that because I'm not sure I understand what this function is
 trying to accomplish. I only know that the function produces a result
 which cannot be true under any circumstances.

 > If you have a patch that includes the modifications, I can bring it in.
 It appears as though the github repo link has not been synced with postgis
 trunk for a couple months.

 At this point, I'm waiting for stability (a beta release to patch
 against). Also, if I recall correctly, my unit tests are written in CUnit,
 for consistency with liblwgeom. We'll either have to leave them behind or
 bring in the CUnit infrastructure to raster.

 Again, I worked out all the equations for the future enhancement on the
 wiki, complete with figures.

Ticket URL: <https://trac.osgeo.org/postgis/ticket/1353#comment:3>
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