What is a Digital Twin?
A digital twin is composed of three parts: a physical product in real space, a virtual product in virtual space, and the connections of data and information that tie the two together.1 The key element that distinguishes a digital twin from a 3D model or a BIM file is the feedback loop — a live, synchronised data connection between the physical and digital worlds.
That distinction matters because the term is often misapplied. Many so-called "digital twins" are actually digital models or BIM files marketed as connected systems, but without any real-time data link.2 A point cloud of a building is not a twin. A static IFC file is not a twin. A digital twin must reflect the current state of its physical counterpart — and update as that state changes.
Why the Feedback Loop Matters
Cities, buildings, and infrastructure are not static. A building's energy consumption changes by the hour. A wildfire perimeter shifts by the minute. A housing market evolves by the month. A digital representation that cannot update with these changes quickly becomes misleading rather than informative.
The feedback loop closes this gap: sensors, IoT devices, open data streams, and user-generated content continuously feed new information into the model. Decisions made on the basis of that model can then inform action in the physical world — completing the cycle.
CDT's Interpretation
CDT extends Grieves's definition to the AECO context and to the national scale. The platform integrates:
- Physical assets — buildings, infrastructure, landscapes, and urban systems across Canada
- Digital representations — BIM models, GIS layers, point clouds, open data, and documents
- Data connections — live sensor feeds, IoT streams, open data APIs, and user contributions that synchronise the two
This means CDT is not a file viewer. It is infrastructure for managing the relationship between a physical environment and its digital representation over time.
Scale
Most digital twin platforms are built for a single building or a single site. CDT operates across scales in a single session:
| Scale | Data types |
|---|---|
| National | National open data (NRCan, Statistics Canada, Open Government) |
| Country subdivision (provincial/territorial) | Provincial and territorial open data portals |
| Municipal | City open data, zoning, parcels, infrastructure |
| Campus / district | Federated BIM models, site surveys |
| Building | IFC models, point clouds, sensor feeds |
| Element | IFC property sets, real-time sensor readings |
Zooming from a national map view into a structural element's property set without switching applications is what CDT is designed to enable.
Open vs. Proprietary
Commercial digital twin platforms — like Digital Twin Britain or Virtual Singapore — are powerful but proprietary: the data, the tools, and the infrastructure are controlled by a vendor. CDT takes the opposite approach. Everything is built on open standards and open-source software, which means:
- Data is stored in open formats (IFC, GeoJSON, LAS) and can leave the platform at any time
- The codebase is public and forkable
- No vendor lock-in — if CDT disappears, your data and workflows are still yours
Key Components
CDT exposes the digital twin through three specialized viewers:
- Map Viewer — MapLibre-powered 2D/3D web map for GIS data, city models, and open data layers
- BIM Viewer — open-source IFC engine (That Open Company) for loading and inspecting building models
- Point Cloud Viewer — Potree-based viewer for large LiDAR and photogrammetry datasets
All three viewers draw from the same underlying project data and share a coordinate system, so a building uploaded in the BIM viewer appears in its correct geographic position in the map viewer automatically.