From kilian.demeulemeester at yellowscan-lidar.com Tue Feb 16 01:01:03 2021 From: kilian.demeulemeester at yellowscan-lidar.com (Kilian Demeulemeester) Date: Tue, 16 Feb 2021 10:01:03 +0100 Subject: [Geotiff] Encoded projection using GTIFSetFromProj4 are specified as USER-DEFINED Message-ID: <96e659e5-6e81-96d8-8b0d-2d15e06208f3@yellowscan-lidar.com> 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-Cl?ment-De-Rivi?re - France Tel: +33 (0)4 11 93 14 06 yellowscan-lidar.com [https://yellowscan-lidar.com/] -------------- next part -------------- An HTML attachment was scrubbed... URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: x-disclaimer-534644925-0.png Type: image/png Size: 1125 bytes Desc: x-disclaimer-534644925-0.png URL: