Scan to BIM Best Practices by Dan Edleson

Whenever you are working in Revit it is helpful to have a list of best practices. Some of the things that come up on typical projects are linking DWGs instead of importing them, using office standard families and organizing views into working and printed. A Scan to BIM model eventually ends up in the same place – a clean Revit model for documentation –but it takes a wildly different way to get there. Here’s some Scan to BIM Best Practices that I’ve found help to keep the process smooth and efficient and prevent major issues with modeling.

1. Limit the View Range

There is so much information in the scan data, if you don’t limit the range of your view you are going to spend a lot of time trying to figure out exactly what you are looking at. In the context of a section all you need to do is change the Far Clip Offset to 1’ or less to keep things tight. Since the section is shown in plans it’s easy to understand where you are cutting and be precise. Modifying the range in a floor plan takes a bit more work.

To modify the Cut Plane in a floor plan you need to edit the View Range. A floor plan in the context of construction documents is typically cut somewhere around 4’ offset from the floor but that may not be where the most accurate data is in your scan. If you have 3’ tall windows with a 2’6” sill height and your view is set to cut off at 4’, suddenly the only thing you are looking at in a lot of places is the thickness of the window, without the wall. So there is a fine balance, especially in plan, about how you set the view range. In general I would say a 1’ or less clip is best for modeling off a point cloud, but you should always double check with a section box in 3D to be sure you aren’t obscuring critical elements.

2. Marking Unknown Thicknesses in Walls

If the scan technician can’t get themselves or their equipment into a space it won’t be scanned. This often leaves blind spots in the scan data that will have to be verified another way. When you encounter these situations it’s important to clearly mark that the thickness you are modeling is a guess. The best way to do this is with a specific wall type and giving it a generic material that graphically shows as a red crosshatch when cut. What I usually do is create a wall type with two layers – finish and unknown. I will put the finish thickness as my best guess (for example if it is gypsum board I’ll make that layer 5/8”) then I will make the unknown layer 3” so the graphic display clearly shows up on all plans. If necessary you can do the same thing with ceilings and floors.

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