[PostGIS] #5735: ST_TRANSFORM uses Helmert transformation instead of NTV2 grid (SRID's : 3812 <->31370)

[PostGIS]

#5735: ST_TRANSFORM uses Helmert transformation instead of NTV2 grid (SRID's :
3812 <->31370)
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 Reporter:  martinvdb                  |      Owner:  pramsey
     Type:  defect                     |     Status:  new
 Priority:  medium                     |  Milestone:  PostGIS 3.4.3
Component:  postgis                    |    Version:  3.4.x
 Keywords:  ST_TRANSFORM Belgium NTV2  |
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 When I want to transform coordinates of objects stored in Lambert72 (SRID
 : 31370) to Lambert2008 SRID : 3812), the ST_TRANSFORM function uses the
 Helmert transformation.
 However there is a more precise trasformation using the NTV2 grid. I
 managed to create that transformation using the new ST_TRANSFORMPIPELINE.
 However, when I try this transformation in PROJ, the default
 transformation is the most precise one using the NTV2 grid.
 My questions are :
     Why ST_TRANSFORM still use this old unprecise method?
     Can I change the behavior of the ST_TRANSFORM to perform the
 transformation using the NTV2 grid?
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Ticket URL: <https://trac.osgeo.org/postgis/ticket/5735>
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