Construction Architect/Architectural Technologist. Founder of Topo-grapher, making accurate site terrain accessible to architects without GIS. Studied in Edinburgh, Copenhagen and Iceland.
The question "which terrain format should I use?" usually gets answered with "whatever your software opens". That is how teams end up with a terrain that opens fine and cannot be edited, or one that is editable but 300 km from the building. The format decides
Most explanations of the Toposolid still describe it as "a Toposurface with thickness". That was roughly true in Revit 2024, when the element first shipped. It undersells what it has become. Since then Autodesk has added excavation, recessed sub-divisions, configurable point limits and better cut and fill
"DEM" and "DTM" get used as if they mean the same thing. Sometimes they do. Sometimes the file labelled DEM includes every tree canopy and roof on your site, and the terrain you import into Revit is a few metres too high in exactly the places
Most "GIS for architects" articles stop at the idea: GIS holds the data, BIM holds the design, connect them. Then nobody tells you which buttons to press. This post does. It takes a national terrain model from download to an editable surface in Revit, Rhino or SketchUp, using
Most Revit site tool reviews were written before Revit 2024 and still talk about Toposurfaces, Building Pads and Graded Regions as if nothing changed. A lot did. Revit now has a solid terrain element, excavation, recessed sub-divisions and configurable point limits, and a review that ignores them will steer
A terrain model can be accurate enough to test building levels, access routes and drainage intent long before a surveyor visits site. But do site models need surveys before they are useful? No. Before they inform a planning submission, set-out or construction decision? Usually, yes. The distinction is not
A Norwegian site can change level dramatically within a few metres. That makes a Norway elevation data guide less about finding a terrain image and more about establishing whether the data is fit for setting out a building, testing access, studying drainage, or coordinating with civil information. For BIM teams,
A terrain model can look convincing while being useless for design decisions. If its levels are guessed, its scale is unclear, or its mesh is too dense to edit, it will not help with a retaining wall, accessible route, drainage fall or building setting-out. SketchUp Sandbox contours are useful
A topographic survey in a BIM model should do more than shade the ground. It should give the design team editable terrain in real-world coordinates, accurate enough vertically and horizontally to test levels, drainage routes, retaining edges and how the building sits, before any of those things get expensive
A site model can look convincing and still be wrong where it matters. A road threshold sits 400 mm higher than the drawing assumes. A shallow swale that carries water off the plot disappears into a smooth, low-resolution surface. A proposed floor level ends up with no dependable relationship
A terrain model can look credible while being wrong where the project needs certainty: at a proposed threshold, along a drainage route or across the interface with a public highway. UK elevation data sources vary significantly in resolution, date, ground classification and coordinate reference. Selecting the right one is less
A pair of coordinates can identify a site precisely, but they do not yet describe the ground your building needs to sit on. To convert coordinates into terrain for BIM, you need three things: the correct horizontal reference system, reliable elevation coverage, and an export that your modelling software can