[postgis-devel] [PostGIS] #1742: PostGIS 2.0 alters Z-coordinate

[Jose Carlos Martinez Llario]

On 30/03/2012 21:16, PostGIS wrote:
> #1742: PostGIS 2.0 alters Z-coordinate
> -----------------------+----------------------------------------------------
>    Reporter:  pramsey   |       Owner:  pramsey
>        Type:  defect    |      Status:  closed
>    Priority:  critical  |   Milestone:  PostGIS 2.0.0
>   Component:  postgis   |     Version:  2.0.x
> Resolution:  invalid   |    Keywords:
> -----------------------+----------------------------------------------------
>
> Comment(by pramsey):
>
>   Oh, and a note to the original poster, you can get back the "old"
>   behaviour (not doing an ellipsoid shift, even though one should be
>   applied) by changing the proj4text in your spatial_ref_sys table and
>   removing the to_wgs84 parameter.
>
The problem is the Z coordinate uses another datum, its does not have to 
be related 100% with spheroid but with geoid.
It should be the user decision. Anyways towgs84 parameters or NTv2 
parameters are needed for grid shift to change the datum and we must not 
remove them if we do then we are just making everything wrong.

Need to do more tests, for example just with 5 parameter transformation 
mb Z might not change? but just guessing.
I ll check if it is chaning too with ntv2 grids if does then we must 
avoid the behavior.

regards,
Jose