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  • EsriReprojector: what's the difference between geographic transformation Amersfoort_To_WGS_1984_NTv2 and Amersfoort_To_WGS_1984_2008_MB?

I'm using the EsriReprojector with source RD_New to destination GCS_WGS_1984 and geographic Transformation Amersfoort_To_WGS_1984_NTv2. Later I need my features to go back to RD New so I use the EsriReprojector again with the source and destination switched and the geographic transformation direction set to Reverse. But this gives me a different coordinate system: _Netherlands-RDNew-2008_0 instead of Netherlands-RDNew-2008 (what it used to be). Why is this a problem? Everything is projected with an offset of 100m. 

 

When using geographic transformation Amersfoort_To_WGS_1984_2008_MB in reverse it seems to be fixed. Yet it still gives me the new coordinate system _Netherlands-RDNew-2008_0

 

Why, how, and will this give me problems when overwriting layers with Netherlands-RDNew-2008? 

 

Any dutchies with the same question? 

Hi @zoedongen​,

When FME reads from an Esri format, it creates a copy of the source coordinate system with the leading and trailing underscores, and a custom mapping to Esri WKT for that coordinate system. We do this to ensure that fi the data is written back to an Esri format, it get exactly the same coordinate system WKT it started with. The EsriReprojector does the same thing to store the Esri WKT from the chosen output coordinate system. This coordinate system is exactly the same as the one without the underscores, except for the WKT it is mapped to.

 

The shift you are seeing seems to be due to an issue with the EsriReprojector in FME 2021, which is applying the transformation grid in the wrong direction when reprojecting back to RD_New. This issue has been fixed in the FME 2022 beta, which can be downloaded from safe.com/beta

Hi @daveatsafe​ Thank you for your response!

It's clear now why it adds the underscores, and its good to know that it's a bug with reprojecting back to RD_New. I'll update to 2022 soon.

 

 

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