Georeferencing

The Georeferencing panel (tab EM, sidebar of the 3D Viewport) is the single place where you anchor your EM scene to a real-world coordinate reference system (CRS). It exposes four canonical values — EPSG, Shift X, Shift Y, Shift Z — which are stored on the Blender scene (scene.em_georef) and propagated, when present, to the companion add-ons that consume them:

When neither add-on is installed, the Georeferencing panel is still the authoritative record of your scene’s CRS — the values persist inside the .blend file and travel with the project.

When to use it

Open this panel before importing GIS layers, georeferenced DXF files, or aligning proxies to surveyed coordinates. Setting the CRS afterwards forces a manual reconciliation against geometry that is already in the scene.

Panel controls

Editable fields

  • EPSG — the EPSG code of the projected CRS (e.g. 32633 for UTM 33N, 3003 for Monte Mario Italy 1, 4326 for WGS84 geographic). Stored as a string; do not prefix with EPSG::.

  • Shift X / Y / Z — the Easting, Northing and Elevation offsets applied to the scene origin, in CRS units (typically meters). The typical archaeological convention is to subtract a “false origin” close to the site to keep Blender working with values below 10,000 m.

Sync status (semaforic indicators)

A small box reports the alignment between EM Tools and each companion add-on:

  • green — add-on installed and its state matches the EM Tools values (within a 1 mm tolerance).

  • yellow — add-on installed but has no CRS / no origin set yet.

  • red — add-on installed and its values diverge from EM Tools.

  • grey — add-on not installed (or not detected). The panel still lists which integrations would become available when present.

Actions

  • Import shift.txt / Export shift.txt — read or write the 3DSC shift.txt file (format EPSG::NNNN X Y Z) so the same shift travels with a folder of meshes.

  • Propagate coordinates — push the EM Tools values to every detected companion add-on.

  • Pull from BGIS / Pull from 3DSC — re-read each add-on’s state into EM Tools, useful after editing the BGIS GeoScene or 3DSC scene properties directly.

  • Push to GeoNode — write the current values into the GeoPositionNode of the active graph, so the absolute position travels with the GraphML when exported.

Advanced

A collapsible section exposes two opt-in toggles:

  • Move objects on origin change — when editing the shift, also translate existing top-level objects. Off by default: most archaeological scenes already contain shifted geometry, and the origin edit is a metadata change, not a transform.

  • Compute lat/lon (needs PyProj) — also derive scene lat/lon from the projected origin via BlenderGIS reprojection. Requires GDAL or PyProj inside Blender’s Python; off by default.

BlenderGIS integration tutorial

BlenderGIS is a third-party Blender add-on that adds GIS data import, basemap visualization, and geospatial operations directly inside Blender. It is the recommended companion add-on for any EM workflow that involves territorial context — landscapes, multi-site projects, or any reconstruction that needs to sit on a real terrain.

This tutorial walks through how to bring BlenderGIS layers into a georeferenced EM scene.

Step 1 — Install BlenderGIS

Download the latest release from github.com/domlysz/BlenderGIS and install as a regular Blender add-on (Edit → Preferences → Add-ons → Install…). Enable it.

Once enabled, the EM Tools Georeferencing panel will detect it and the BlenderGIS sync indicator will turn yellow (installed, no values yet) or green (installed, values already coincide with EM Tools).

Step 2 — Configure the EM scene georeferencing

In the Georeferencing panel of EM Tools, set the four canonical values:

  • EPSG of your project (e.g. 32633 for UTM 33N, 3003 for Italian Monte Mario zone).

  • Shift X / Y / Z — typically the Easting / Northing / Elevation you subtract from absolute coordinates to keep your scene around the world origin.

These four values are the contract that BlenderGIS will honour when projecting incoming layers into your scene. With the panel update callback in place, simply editing them pushes the values into the BlenderGIS GeoScene automatically (no manual sync needed). If the sync dot stays red, click Propagate coordinates to force-push.

Step 3 — Import GIS layers

Use BlenderGIS’s native import flows:

  • Shapefile (.shp) → GIS → Import → Vector

  • GeoTIFF rasters (terrain DEM, orthophoto) → GIS → Import → Georaster

  • Web map services (Bing, OSM, Mapbox, …) → GIS → Web geodata (network required, plus an access key for some providers).

BlenderGIS reads the source CRS from each file (or asks you to specify it for shapefiles without a .prj sidecar) and reprojects on import into the scene’s EPSG, applying the origin offset you set in EM Tools.

Step 4 — Integrate with EM proxies

Now that your scene carries georeferenced layers, your EM proxies (walls, structures, surfaces) are positioned in absolute coordinates. Typical follow-up moves:

  • Use orthophotos as visual references for re-modelling existing structures.

  • Build proxies that align with surveyed terrain elevations sampled from a DEM.

  • Cross-reference findings from multiple sites within the same territorial context, by overlapping their proxies on the same BlenderGIS basemap.

When you export the scene to Heriverse or to a GraphML for documentation, the georeferencing travels with the project — the GeoPositionNode (push via the Push to GeoNode button) is the canonical place in the graph where the CRS+shift live.

Notes

  • BlenderGIS is maintained by an external community, not by the EM team. For tool-specific issues (failed imports, CRS conflicts, performance with large rasters), consult the BlenderGIS documentation or its issue tracker.

  • The EM Georeferencing panel is the source of truth for the scene’s CRS. If BlenderGIS suggests reprojecting to a different CRS, prefer to keep BlenderGIS aligned to the EM panel’s EPSG rather than changing the EM-side reference (which would shift every existing proxy).

  • For non-UTM CRS reprojection, BlenderGIS needs GDAL or PyProj installed inside Blender’s Python. The Compute lat/lon toggle in the Advanced section relies on the same dependency.