Over the weekend, I converted the old XSLT 2 code to create GeoJSON to XSLT 3, which means it's much easier to add more support for new TEI elements being converted to HTML in the GeoJSON, and to debug that whole module. Today I've added a new test project based on static image markup, and started extending the code so that it can tell the difference between when it's working on static images (using only pixel offsets) and when it's working on a genuine map (in which case various conversions have to happen between projections, since we render in EPSG:3857 but store in EPSG:4326 for GeoJSON conformity). I'm about a third of the way there, but so far it's very promising.