To reproject WGS84 (Lat/Long) to GDA2020 (Easting/Northing) in FME v2024.1, the only option appears to be via GDA94. This moves the data approx. 1.8m NE as it assumes that WGS84=GDA94 and GDA94+1.8m = GDA2020.
While this is usually what people use, there is a need for a second option of WGS84=GDA2020 (ie a Null transformation + Geographic to Grid) as other software packages, such as Conquest have adopted this. For more information see: https://www.spatial.nsw.gov.au/__data/assets/pdf_file/0008/224396/WGS84_and_Australias_misaligned_web-maps_Information_Sheet.pdf.
Is this something that FME will be implementing anytime soon?
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Gosh I had lots of fun with GDA2020 to WGS. My main learnings were to be careful where you specify Coordinate Systems. Also… read the transaction log in detail and in sequence. It tell you what user specified transformation was used where.
Implicit approach is to “Read from Source” and don’t specify the destination coordinate system = “Same as Source”.
Explicit approach is to either specify the destination Coordinate System explicity OR to use one of the four reprojector transformers and explicitly reproject the data before writing it out with no value in the writer (don’t double up in transformer AND writer - this causes issues/misinterpretation for the fme engine.
Reprojecting data requires transforming between datums
Two types of datum transformers
1.Mathematical
•Three parameter (Geocentric)
•Four Parameter
•Seven Parameter (incl Burda/Wolf)
•Ten Parameter (Molodensky-Badekas)
2.Adjustment Grids
•NTv2
•NADCON
I found the best approach was if they were ESRI licensed users, then promote use of EsriReprojector with library GDA2020 to WGS 84 (2). GDA2020 & WGS84 (Web GIS) - Esri
In terms of CSMapReprojector, there are issues/bugs relating to GDA2020 that are resolved in 24.1 release. I avoid the single Multistep’ transformation option in this transformer. Use the libraries with the MGA word, over simply choosing the EPSG number; that way you are presented with grid transformation options like 7P o Ntv2.
I prefer to use 2 x CSMapReprojectors.
The first takes the incoming MGA2020, reverses the shift to GDA94 using 7P as a default. The NTv2 exists if the data needs to move/adjust it 1.8m (READ the LOG for the shift file used) due to previously being introduced when the data first got written to GDA2020.
The second uses a <None> / NULL transformation to take GDA94 to WGS84
Lastly, give the ProjReprojector a try, its definitely got GDA2020 libraries in there
