Edge-Based Close-Range Digital Photogrammetry for Structural Deformation Measurement

Abstract

This paper proposes a close-range digital photogrammetric system based on edge detection for structural deformation measurement. Different from traditional photogrammetric applications using discrete points, continuous edges in digital images are used here as the controlling feature in this new system. This makes it possible to acquire spatially intensive information. The system uses several digital images of the structure, taken from a number of different stations before and after the deformation is induced. Then, an image-matching algorithm based on the coplanarity condition developed here is applied to establish spatial relationships of the interested edges, identified by using a new high-precision method. These relationships are subsequently employed to acquire full-field deformation measurement of the structure. A series of experiments was conducted in the laboratory to investigate the capability of the new photogrammetric system. Results show that the system is highly accurate and suitable for structural deformation measurement. It offers noncontact, full-field, and spatially intensive measurement, in contrast with conventional contact and point-measurement.