AS-BUILT 3D MODELING BASED ON STRUCTURE FROM MOTION FOR DEFORMATION ASSESSMENT OF HISTORICAL BUILDINGS

Abstract

Assessing the state of historical buildings is non-trivial tasks as limited information is available
and only non-invasive assessment can be performed on these buildings. Image-based 3D reconstruction is a
recent technique, which can construct an as-built model of a historical building to be used for damage and
deformation assessment. The technique is based on Structure from Motion, which can automatically create a 3D
model from uncalibrated images. In this paper, VisualSFM, automated image-based 3D modeling software, is
applied to construct a 3D model of a historical building. The model is compared with a model obtained from a
laser scan (LIDAR). To perform a deformation assessment on the building, a series of a horizontal plane is sliced
through the 3D model, and then a centre of each 3D slice is joined to form a line representing an incline angle of
the building. This technique is performed against a laboratory dataset to determine its accuracy. It was found that
for a small incline angle (less than 4o), the technique contains the inaccuracy of 2.75% with increasing
inaccuracy as inclined angles become larger. When applying the technique to a real temple dataset, it was found
that the angle of inclination is less than 3o, which is in an acceptable range for the proposed technique.
Additionally, it was found that the inclined angles obtained from VisualSFM and LIDAR are almost identical. It
was recommended that VisualSFM can be used instead of LIDAR when performing damage assessment in
historical buildings.