Is Your BIM Right?

Tom Greaves, Chief Marketing Officer - DotProduct Boston

​How seductive?  The clean lines, crisp angles and photorealistic textures of a well executed Revit model catch your eye and make you wish the real world was half as pretty. However, beware the treachery that sometimes lurks within. 

A couple of weeks ago we scanned a training room at Modena’s facility in Cape Town, South Africa with a new DPI-8X handheld.  Just to check, we brought the scan data into Revit to compare the as-built with the Revit model of the building.  The scanning part took about 15 minutes, which included putting up and measuring a few targets with a Leica S910 Disto – more about that later. Then we pulled up the Revit model and extracted the northing, easting and elevation of one of the windows.  We used this to set the coordinate system on the point cloud.  All of this took another 5 minutes. Then we took the point cloud into Autodesk ReCap and from there exported it to the Revit model for comparison and editing.

What we found:

• The length of the training room was off by 700mm (28 inches).  We verified the point cloud using the Leica disto.
• The window we used to register the point cloud to the revit model was off about 300 mm (12 inches) from the correct location. 

 
Mitch Parsonage who delivers Revit training courses for Modena updated the Revit model on the spot. See the video – this part was very fast.  From a cold start, we had an updated Revit model in less than 30 minutes and this included some on-the-job training.
 
What did we learn?

• Trust but verify.  If your Revit model looks good, you ought to check it anyway.  This example is not isolated and there are often very good reasons for the as-built to be different than the design model.
• Checking and updating a Revit model is fast and cost effective and can be done by non-specialists.  It used to be that you would schedule a laser scanning crew, get them to come to your site, have them scan your project and then have them send you the model 2 days later (or 2 weeks).  Today we can execute this for small projects in minutes.  The DPI-8X scanner costs about the same as mobilizing a laser scanning crew for one small project.
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It’s all about the workflow.  Scanning, registration, bringing the data into Revit and then fixing it can be done quickly once you’ve had a little training and some practice.