[Geotiff] Encoded projection using GTIFSetFromProj4 are specified as USER-DEFINED

[Kilian Demeulemeester]

Hi everyone,

I am willing to write down geotiff files.

For instance, i'd like to encode the projection info |EPSG:25831|.

In order to write down the projection in the geotiff, I am using 
|GTIFSetFromProj4(gtif, proj4String)|.

In order to use this method, I first convert |EPSG:25831| to it's proj4 
equivalent via the method |proj_as_proj_string| (proj library)

This convert |EPSG:25831| to |+proj=utm +zone=32 +datum=WGS84 +units=m 
+no_defs +type=crs|

The encoded information are the following;:

|Geotiff_Information: Version: 1 Key_Revision: 1.0 Tagged_Information: 
ModelTiepointTag (2,3): 0 0 0 571239.5625 4845679 0 ModelPixelScaleTag 
(1,3): 2 2 0 End_Of_Tags. Keyed_Information: GTModelTypeGeoKey 
(Short,1): ModelTypeProjected GeographicTypeGeoKey (Short,1): 
User-Defined GeogGeodeticDatumGeoKey (Short,1): User-Defined 
GeogEllipsoidGeoKey (Short,1): Ellipse_GRS_1980 ProjectedCSTypeGeoKey 
(Short,1): User-Defined ProjectionGeoKey (Short,1): User-Defined 
ProjCoordTransGeoKey (Short,1): CT_TransverseMercator 
ProjLinearUnitsGeoKey (Short,1): Linear_Meter ProjNatOriginLongGeoKey 
(Double,1): 3 ProjNatOriginLatGeoKey (Double,1): 0 
ProjFalseEastingGeoKey (Double,1): 500000 ProjFalseNorthingGeoKey 
(Double,1): 0 ProjScaleAtNatOriginGeoKey (Double,1): 0.9996 End_Of_Keys. 
End_Of_Geotiff. |

Unfortunately, in QGIS (my version is QGIS 3.6), the detected CRS is a 
"generated CRS" and not "EPSG:25831".

What I am doing wrong? Most of the time, our user will choose the 
projection from the EPSG database, so I always have the EPSG code 
available if needed.

I am using proj7 and libgeotiff 6.0.

Thank you very much

Kilian



Kilian Demeulemeester
Software Project Lead - R&D

[https://yellowscan-lidar.com/]

525 Avenue Saint Sauveur du Pin
34980 Saint-Clément-De-Rivière - France
Tel: +33 (0)4 11 93 14 06
yellowscan-lidar.com [https://yellowscan-lidar.com/]
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