If you prefer, you can read the article in PDF here: tcpMDT-Revit integration: how to carry a digital model with real coordinates.
By Francisco Navarrete Mandly
Bringing a digital terrain model (DTM) from a CAD/topographic environment to Revit is an increasingly common step to define the grading where a building will be supported, develop and coordinate the layout of roads and the urbanization of the site, obtain measurements, improve 3D visualization, check for clashes and deliver an IFC to third parties.
The challenge is that Revit handles the site and geometric references with a different logic than a traditional CAD flow, and that directly affects origins, base points, shared coordinates, precision limits, and the final result.
1. Need for this exchange and difficulty in choosing the right alternative
Integrating a terrain created in tcpMDT into Revit seems, a priori, a "simple" operation: export and import. In practice, the real difficulty lies in the number of possible combinations and in the fact that each decision (format, geometric content, whether to import or link, how to position and how to solve coordinates) changes the behavior of the model.
1.1. Alternatives and Additional Licenses
For years, LandXML-based streams for exchanging survey data (often using plug-ins) existed in certain Revit environments and versions, but they have not always been available or consistent across versions. In parallel, many "classic" land-BIM integration flows are supported by other Autodesk applications such as Civil 3D or specific extensions.
Precisely for this reason, a key advantage of this article is that it summarizes two practical workflows that do not require additional licenses to perform the basic exchange (beyond tcpMDT and Revit), avoiding relying on external tools to obtain usable terrain in Revit.
1.2. CAD or IFC
🔹 CAD option (DWG/DXF): Here you must choose which representation is exported from tcpMDT and with which objective in Revit. In CAD, terrain can be represented as a point cloud, 3D faces, polyface meshes, or contour lines.
🔹 IFC option: if the objective is BIM interoperability, the IFC provides structure and traceability, but also opens up another range of decisions: IFC 2×3, IFC 4 and IFC 4.3. And again, the critical question arises: how Revit will interpret the location and coordinates of the IFC.
1.3. Import or Link
🔹 Linking is usually the safest option for coordination (updates, link download, phased control).
🔹 Importing can "consolidate" geometry within the RVT, but it can also make the update flow more rigid.
1.4. Coordinate systems
In real coordination there are many variants: automatic positioning (by center, by origin, by shared coordinates if they exist) and manual positioning (consciously placing and adjusting).
Here a recurring problem appears: if the original file is in global coordinates (UTM/ETRS, etc.) and arrives in Revit "as is", it is very common for incidents to arise (huge distances from the Internal Origin, precision difficulties and strange graphic behavior).
2. Proven exchange flows
The following describes two reproducible workflows for bringing a terrain model from tcpMDT to Revit. Each one indicates the typical objective, the steps and the critical points that usually cause incidents.
2.1. CAD Drawing with 3D Faces
This flow is recommended when you want to convert the terrain into a native Revit element (toposolid) to work with the site, visualization and coordination in a direct and controlled way.
🔹 In tcpMDT, draw the surface as 3D faces and save the drawing.
🔹 In Revit, create a project and Link CAD to the DWG file. The example uses units in automatic and source-to-internal positioning.
🔹 Go to Massing & Site → Toposolid → Create from Import. On the Modify menu, run Create a Toposolid from Import, and choose Create from CAD to get the solid.
Figure 1. MDT Surface converted to Toposolid in Revit
Video 1: tcpMDT to Revit Surface (link)
2.2. IFC File
This flow is especially suitable when the exchange has a clear BIM objective (delivery, coordination or federation) and you want to convert the terrain to a standard format, while maintaining georeferencing in a controlled way.
🔹 In tcpMDT, set the coordinate system of the project.
🔹 When exporting, indicate a reference point of known coordinates and enable the Draw Reference Point option. Select the IFC version 4.3 Add2.
🔹 In Revit, link the IFC (Insert → Link IFC) to maintain an updatable and coordinating flow.
🔹 Place the IFC with an explicit criterion (e.g., IFC Origin to Project Base Point) and visually check the position using the exported point.
🔹 Check the units of the project and make sure to work in meters before setting coordinates, to avoid scale inconsistencies.
🔹 Set the actual coordinates: Manage → Coordinates → Specify coordinates at point, select the reference point, and enter its XYZ values.
🔹 Check the result by placing a point coordinate annotation/elevation and review properties to confirm that coordinates and orientation are consistent.
🔹 Maintain the IFC as a link: If IFC reviews are received, it must be reloaded and validated again against the same benchmark.
Figure 2. MDT Surface converted to Revit using an IFC file, in real coordinates
Video 2: IFC generated with tcpMDT to Revit (link)
3. Coordinate Origin
In Revit, the model's location is articulated around three complementary references: Internal Origin, Project Base Point, and Survey Point. When you create a new model, the Project Base Point and the Survey Point default to the Internal Origin.
3.1 Internal origin
The Internal Origin is the "fixed" reference of the model. Revit works on a modeling work area of 20 miles (32 km) in diameter; therefore, all model geometry (including links and imports) must be within a 10-mile (16 km) radius of the Internal Origin. If this limit is exceeded, the graphical representation may be less reliable and accurate.
3.2 Project Base Point
The Project Base Point establishes a baseline for measuring distances and placing objects in the context of the model. When starting a project, it is recommended to decide where to place it and agree on it as a team so that everyone works with the same reference point.
3.3 Survey Point
The Survey Point defines the origin of the coordinate system and provides real-world context (for example, a corner of the site or the intersection of two boundaries). In addition, when importing or linking models, it can be used as a reference for alignment along with the concept of shared coordinates.
3.4 Project North and True North
It is convenient to distinguish Project North/True North because it affects the orientation of views and the reading of coordinates", supported by the best practices of coordinates in Revit.
4. Conclusions and recommendations
If you need a native and editable terrain within Revit (Toposolid) to work on the site and coordination, the most direct option is the CAD flow using 3D faces, since Revit allows you to generate a Toposolid from imported CAD data/linked with 3D information.
On the other hand, if the priority is BIM interoperability and delivery or coordination in IFC with verifiable georeferencing, the most robust is the IFC flow supported by a reference point exported from tcpMDT.
Finally, it is recommended to document (in a coordination note) units, reference system, control point and positioning option used, so that each terrain update can be recharged without surprises.
References
tcpMDT Professional Product Page
tcpMDT OpenBIM Features
BIM for Surveyors
IFC Road Project
ROADBIM Project
