Show ArcGIS Online service transformation definitions and allow for configuration through UI

[ChristopherCounsell]

Services that do not match the Web Map basemap coordinate system will be projected to align. If a transformation is required, a default transformation will be selected unless a datumTransformation is specified on the service from the time of publish. 

This means that a user could have two 'GDA94' feature services. One published with no transformation (defaulting to 'GDA94 to WGS84 2') and another published with the old transformation ('GDA94 to WGS84'). The first will align data to WGS84@GDA2020 and the second will align to WGS84@GDA94, resulting in a 1.8m offset.

The end users can see that the services are both GDA94 but the only way they can identify the datumTransformation set from the time of publish is via the Admin REST API. Or externally supplied metadata.

It would be great if we can:

• Show the datumTransformation set for a service at the publicly accessible REST level or item details page
• Allow ArcGIS Online publishers to manually change the datumTransformation via the configuration user interface instead of having to invoke Admin REST API definition updates.

Coordinate systems and projections are intro-level GIS and we are relatively hamstrung to get data to align without the above. Sure we could improve publishing workflows, but what about external service providers? How do I know what transformation is set for a government ArcGIS Server service unless they have volunteered this information in the details or via their site?

https://doc.arcgis.com/en/arcgis-online/reference/faq.htm#anchor69

https://www.esri.com/arcgis-blog/products/data-management/data-management/taking-control-of-transfor...

[ChristopherCounsell]

Formal enhancement request is ENH-000143531. Lodge a support case with Esri and attach yourself to it if you're interested in seeing this come out!

[ChristopherCounsell]

@GordonSumerling @GlenShepherd  share some love on this one and I'll do another blog post 😉

[PeterMacKenzie2]

I followed the Option 2 steps here:
FAQ

with the intent to transform my GDA2020 (7854) data into WGS84 Auxillary. (3857) using WGS 84 to GDA2020 (3) [9690] at the publish to Hosted Feature Layer  step into AGOL. Used Pro 3.2.1

My rest/admin/services/ URL still reports Spatial Reference: 7854 (7854)

Does this mean my HFL is in 7854 and IS being re-projected on the fly using the 9690 transformation?
Or does this mean it has published but not honored the transformation?
How can you tell?

[ChristopherCounsell]

The NTv2 grid based transformations for Australia aren't default in ArcGIS.
They won't be supported in ArcGIS Online.

You need to set your map to web Mercator and project your data
before/during publish. If your map is different to the data, the service
will adopt the map and project your data during publish using any
transformations set in the map properties at the time.

[PeterMacKenzie2]

Thanks for the reply Chris. 
I was jumping between Enterprise and AGOL and got my wires crossed. 
I have applied the transformation in my Pro map as suggested and checked my rest end point  and can see that it has correctly published as 3857.