There is a guide about creating new ones:

https://docs.safe.com/fme/html/FME-Form-Documentation/FME-Form/Workbench/coordinate_sys_custom_about.htm

I have never needed this, so I have no idea how complex it is to create a new one.

I’m loath to create cutom definitions of things that are already authoritatively described. That bakes in opportunities to make mistakes from typos and what not (in addition to simply being cumbersome). That said, it’s good to know this path exists when really needed.

Yeah, I know the feeling 

Unless anyone has a better way, you could create an Idea asking Safe Software to add them: https://community.safe.com/ideas

It is not a given that they would add them, but at least they’ll read the request.

Here’s an existing idea for this:

Hi @mattwilkie,

The Coordinate System Gallery applies to the CSMAP reprojections engine, which was the first reprojection engine added to FME, and is used in the Reprojector, CsmapReprojector and implicit reprojections triggered by setting the output coordinate system on a writer. However, the PROJ reprojection engine, utilized in the PROJReprojector transformer, seems to have more up to date EPSG coordinate system definitions.

If you can’t find the particular EPSG coordinate system you are looking for in the Coordinate System Gallery, please try using the PROJReprojector instead.

Thanks Dave, I didn’t know that and will file that away for remembering when needed later. However in the case that sparked this thread neither of those transformers are being used. I’m joining 2 source layers - a feature class and a shapefile - that have identical but differently named coordinate systems, and FME is not liking that. I’m overriding via Coordinate System parameter but can’t use the right EPSG code.

Hi @mattwilkie,

There are a few things you can try in this case:

1. CSMAP has many coordinate systems that are not mapped to EPSG codes. Check the incoming coordinate system parameters to see if you can find a non-EPSG code match.
2. Create a new coordinate system from the Shape file PRJ file, using the online app at fme.ly/coordsys. If you copy the contents of the PRJ file into the Esri WKT box on the first page, the app will try to autogenerate most of the new coordinate system settings for you. Check the accuracy of these settings on the second page, add a name and EPSG code, and you have the new coordinate system you need.
3. FME will create temporary coordinate systems from both the Shape and feature class input when reading them, and the names will be consistent from run to run. Use the Data Inspector to see what coordinate system name is given to the feature class, then use a CoordinateSystemSetter on the Shape data stream to override the coordinate system with that name. You do not have to choose a coordinate system name form the Gallery - you can type directly into the text box (case-sensitive.)