Offline Basemap projection requirement

[GregCarlino2]

If the basemap projection dictates the web map projection, is there a way to take a map offline in a projection other than Web Mercator?  I've sideloaded an raster tile .tpkx in State Plane which I would like to use onto my tablet, and my web map operational layer is in State Plane, as well.  However, I'm stuck with the paradox of having to use a Esri basemap in Web Mercator or WGS84 to enable the 'Offline' setting in the web map item page, but then this causes an error in the 'Offline' section of the Field Maps (Enterprise) app because the web map layers are in different projections.  Is there any way to side-step this initial requirement?

Specs:

Enterprise 10.9.1

iPad Pro - iOS 17.7

[ChristopherCounsell]

https://enterprise.arcgis.com/en/portal/10.9.1/administer/windows/customize-basemaps.htm#ESRI_SECTIO...

1. Publish a new layer in your desired coordinate system that can act as a basemap (e.g. imagery in state plane)
2. Add the layer to your map and choose to move it to your basemap (follow the steps in documentation above). You should not have any other layers in your basemap (e.g. reference).
3. Congratulations, you now have a map with a basemap in state plane.

You will be stuck with that coordinate system. Changing basemaps in field maps will only show others in the same coordinate system (i.e. additional custom maps in your custom basemap gallery, see documentation). But it should work with your raster tile .tpkx.

[GregCarlino2]

Thank you Christopher,

I've added an aerial Map Image in 'Classic' viewer, as per link above, and selecting 'Move to Basemap', but this still does not enable the 'Offline' section in the Item Detail page and still shows an 'X' next to the basemap in Field Maps enterprise app.  Does this solution only work with Image layers?  I do not have an Image Server set up, so I'm stuck with Map Images.

[ChristopherCounsell]

A variety of layers can be used but they need to be configured for offline
use.

For tile layers make sure export of cache is enabled. Similar for hosted or
referenced.

https://enterprise.arcgis.com/en/portal/latest/use/take-maps-offline.htm

[GregCarlino2]

I overwrote the raster map image, enabling export of cache, and built a new tile cache and web map but Field Maps still shows an error with the basemap layer.  After some searching, I was able to find an Esri Basemap (for export) in WGS84, which is at least closer to what I'm looking for.