Butterwick Projects Ltd. Case Study

On the first building, a test for a 51-townhome retro-fit project, the firm used tape measures and levels to collect the desired geometric details. However, this manual process was time consuming and required extensive checking and rechecking to avoid mistakes and inaccuracies, especially in wall corners and window frames. Butterwick’s intention was always to utilize digital data capture for the remaining buildings. For that to work they needed a way to accurately derive building geometry from 3D point clouds. Undet, looked to be the perfect answer.

A local surveyor scanned the next building with a Leica BLK 360 stationary laser scanner and used surveyed targets on the buildings to improve the scan registration. He sent the resulting .e57 file to Amerongen.

Amerongen used the Undet tutorial resources to learn the software and extract the necessary building geometry, especially window and door locations.

To determine if the result was accurate enough for panel design, he took dozens of tape measurements from the building to compare with the Undet extraction. Most were within the hoped for 5 to 6mm. When he double checked the bigger errors, it turned out it was the tape measurements that were wrong. The realization that while a digital scan might have an error of a few millimeters, it would never be off by a foot or on the wrong side of the building gave him the confidence to commission the scan of the rest of the 15-building complex.

Once the wall geometry is extracted by UNDET, he can begin drawing the new panels in SketchUp. The 3D extraction has to be precise because he relies on the existing wall geometry as the base layer to draw the panel details.

Amerongen performs much of his work in UNDET using the Automatic Feature Extraction tools. He simply clicks on any point on an exterior wall, and the software automatically extracts the required wall plane. Two clicks are all it takes for UNDET to create a line representing the exact corner geometry in SketchUp. There are several feature extraction tools depending on the exact task at hand.