Bug#1008612: closed by Sebastiaan Couwenberg <sebastic at xs4all.nl> (Re: Bug#1008612: libspatialite7: erroneous geometry conversion using ST_Transform)

[Sebastiaan Couwenberg]

On 3/29/22 17:35, Brian Miles wrote:
> I apologize that I mis-stated my original description of the bug. It is not that the results for 26910 transforms are the same as for 32610 transforms, but that transforms to 26910 are simply incorrect for Debian/Ubuntu.

I'm no projection specialist, I cannot judge whether a transformation is 
correct or not. The experts for that frequent the proj mailinglist.

> As this is only happening on Debian/Ubuntu, it is not clear to me that bringing this upstream will result in resolution. Are there any other option to addressing this?

Things that may affect the transformation result:

  * libspatialite version
  * proj version
  * whether proj-data grids are installed / PROJ_NETWORK=ON is set

proj-data is not packaged in Debian (#952459), it is packaged in Alpine.

Datumgrid availabilty makes better transformations possible:

$ spatialite /tmp/test.db "SELECT AsText(point), 
AsText(ST_Transform(point, 26910)) FROM test;"
SpatiaLite version ..: 5.0.1    Supported Extensions:
         - 'VirtualShape'        [direct Shapefile access]
         - 'VirtualDbf'          [direct DBF access]
         - 'VirtualText'         [direct CSV/TXT access]
         - 'VirtualGeoJSON'              [direct GeoJSON access]
         - 'VirtualXL'           [direct XLS access]
         - 'VirtualNetwork'      [Dijkstra shortest path - obsolete]
         - 'RTree'               [Spatial Index - R*Tree]
         - 'MbrCache'            [Spatial Index - MBR cache]
         - 'VirtualFDO'          [FDO-OGR interoperability]
         - 'VirtualBBox'         [BoundingBox tables]
         - 'VirtualSpatialIndex' [R*Tree metahandler]
         - 'VirtualElementary'   [ElemGeoms metahandler]
         - 'VirtualRouting'      [Dijkstra shortest path - advanced]
         - 'VirtualKNN'  [K-Nearest Neighbors metahandler]
         - 'VirtualGPKG' [OGC GeoPackage interoperability]
         - 'VirtualXPath'        [XML Path Language - XPath]
         - 'SpatiaLite'          [Spatial SQL - OGC]
PROJ version ........: Rel. 9.0.0, March 1st, 2022
GEOS version ........: 3.10.2-CAPI-1.16.0
RTTOPO version ......: 1.1.0
TARGET CPU ..........: x86_64-linux-gnu
POINT(-122.338928 47.629273)|POINT(549665.158879 5275308.47686)
POINT(-122.338923 47.62927)|POINT(549665.537361 5275308.146648)
POINT(-122.33895 47.629253)|POINT(549663.525012 5275306.240011)
POINT(-122.392051 47.62888)|POINT(545674.479273 5275232.14496)
POINT(-122.392038 47.62888)|POINT(545675.455944 5275232.152617)

$ PROJ_NETWORK=ON spatialite /tmp/test.db "SELECT AsText(point), 
AsText(ST_Transform(point, 26910)) FROM test;"
SpatiaLite version ..: 5.0.1    Supported Extensions:
         - 'VirtualShape'        [direct Shapefile access]
         - 'VirtualDbf'          [direct DBF access]
         - 'VirtualText'         [direct CSV/TXT access]
         - 'VirtualGeoJSON'              [direct GeoJSON access]
         - 'VirtualXL'           [direct XLS access]
         - 'VirtualNetwork'      [Dijkstra shortest path - obsolete]
         - 'RTree'               [Spatial Index - R*Tree]
         - 'MbrCache'            [Spatial Index - MBR cache]
         - 'VirtualFDO'          [FDO-OGR interoperability]
         - 'VirtualBBox'         [BoundingBox tables]
         - 'VirtualSpatialIndex' [R*Tree metahandler]
         - 'VirtualElementary'   [ElemGeoms metahandler]
         - 'VirtualRouting'      [Dijkstra shortest path - advanced]
         - 'VirtualKNN'  [K-Nearest Neighbors metahandler]
         - 'VirtualGPKG' [OGC GeoPackage interoperability]
         - 'VirtualXPath'        [XML Path Language - XPath]
         - 'SpatiaLite'          [Spatial SQL - OGC]
PROJ version ........: Rel. 9.0.0, March 1st, 2022
GEOS version ........: 3.10.2-CAPI-1.16.0
RTTOPO version ......: 1.1.0
TARGET CPU ..........: x86_64-linux-gnu
POINT(-122.338928 47.629273)|POINT(549665.036792 5275308.276363)
POINT(-122.338923 47.62927)|POINT(549665.415273 5275307.94615)
POINT(-122.33895 47.629253)|POINT(549663.402919 5275306.039517)
POINT(-122.392051 47.62888)|POINT(545674.35684 5275231.954471)
POINT(-122.392038 47.62888)|POINT(545675.333511 5275231.962125)

Kind Regards,

Bas

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