Coordinate system error when attempting to switch to a GeoPDF basemap in an offline map

[BradyCallahan]

I'm getting a "Basemap Unavailable - The spatial reference isn't compatible with this map" error when attempting to switch to a GeoPDF basemap in an offline Map.

I created three GeoPDFs in Pro, all at the same time, and side-loaded them to the Basemap folder on my device. They all show up in the Basemap Gallery in Field Maps and work fine in dynamic maps. However, if I attempt to pick one while using an offline map I get that spatial reference error.

I made sure that the Map SRS in Pro was set to WKID:3857 before exporting the GeoPDFs. However, one oddity is that when I brought them back in to Pro, their WKIDs are listed as the outdated Web Mercator tag of WKID:3785.

Anyone else seeing these types of issues or got any ideas?

iOS 26.3.1
Field Maps 26.1.1
ArcPro 3.5

[JonathanLebowitz]

Hello. When authoring the map, was the GeoPDF specified on the Offline page of Field Maps Designer or in the item details of the map per Prepare maps for download? Was the original basemap in the map also in PCS WGS 84 Web Mercator/EPGS 3857? How did you bring the GeoPDF back into Pro?

[BradyCallahan]

 @JonathanLebowitz 

I've tried it by pre-specifying a GeoPDF as the offline basemap in the item details page and also without specifying an offline basemap at all (just using the Map default). Results were the same.

Yes, the original basemap in the map was also EPSG:3857, its the World Imagery layer. My GeoPDF's are just exports of three different ESRI basemaps, Pencil, Antique, and Community. No other layers at all. 

Brought the GeoPDF back to Pro by a drag-and-drop, then checked it's properties through the TOC.

I've been referring to Jeff Shaner's March 2, 2026 blog post about using GeoPDF's

https://www.esri.com/arcgis-blog/products/field-maps/field-mobility/add-geospatial-pdfs-to-your-fiel...

[JonathanLebowitz]

Thank you for clarifying that. You are likely hitting open bug ID BUG-000183698 in ArcGIS Pro. A summary of the bug is as follows: "When exporting a map layout as an georeferenced PDF in ArcGIS Pro, the geoinformation from layers in the WGS 84 / Pseudo-Mercator (EPSG:3857) coordinate system is incorrectly written to the deprecated Popular Visualisation CRS / Mercator (EPSG:3785) coordinate system." Do you have the ability to open a Technical Support case to get attached to the bug? If not, I can share the public bug status link once it becomes available.

The workaround is to use the Project Raster (Data Management) tool on the PDF file to re-project it from Popular Visualisation CRS Mercator/3785 to WGS 1984 Web Mercator/3857. The geographic transformation should automatically populate as WGS_1984_Major_Auxiliary_Sphere_To_WGS_1984, which is a NULL transformation.

[JonathanLebowitz · Accepted solution]

Hi Brady. I realized that the workaround documented in the bug may not be valid for your use case as the Project Raster tool does not support the .pdf file extension for the "Output Raster Dataset," and you are trying to sideload the basemaps onto your devices. Unfortunately, you may need to wait for the bug to get fixed. You can provide additional information about the business impact of the bug in My Esri by following the steps at https://support.esri.com/en-us/knowledge-base/provide-a-business-impact-statement-for-a-bug-00002412... or by contacting your Accounts Team.

[BradyCallahan]

I opened a support ticket and they got back to me with this same information early this morning. I guess this got rolled out a bit prematurely. Bummer.

[BradyCallahan]

Hmmm... I found that I can update the CRS in a GeoPDF using GDAL in Pro

from osgeo import gdal
gdal.Translate('GeoPDF_out.pdf', 'GeoPDF_in.pdf', format="PDF", outputSRS="EPSG:3857")

When I review the output GeoPDF file CRS properties in Pro all looks great and it draws in the correct location in a Map. However, when I bring it into Field Maps I get a slightly different error than before "Basemap Unavailable - The basemap doesn't have a valid spatial reference"

This is odd since it is working correctly in Pro.

[JonathanLebowitz]

Interesting. I wonder if the gdal.Translate() method is somehow stripping the PDF of the geospatial information that Field Maps needs. Is there another format you can specify for "geospatial PDF?"

[BradyCallahan]

I don't know but I just tried bypassing Pro entirely by exporting a GeoPDF using the print widget in an AGOL webmap. I was thinking I'd get a clean file that way. The output draws fine in Pro, CRS looks good. Does Field Maps like it? Nope.

Its starting to seem to me that there's more here than just a BUG with Pro.

[JonathanLebowitz]

Is the behavior any different if you browse for the PDF item in your organization instead of sideloading it?