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Unmanned aerial vehicle (UAV) vision-based sensing has become an emerging technology for structural health monitoring (SHM) and post-disaster damage assessment of civil infrastructure. This article proposes a framework for monitoring structural displacement under earthquakes by reprojecting image points obtained courtesy of UAV-captured videos to the 3-D world space based on the world-to-image point correspondences. To identify optimal features in the UAV imagery, geo-reference targets with various patterns were installed on a test building specimen, which was then subjected to earthquake shaking. A feature point tracking-based algorithm for square checkerboard patterns and a Hough Transform-based algorithm for concentric circular patterns are developed to ensure reliable detection and tracking of image features. Photogrammetry techniques are applied to reconstruct the 3-D world points and extract structural displacements. The proposed methodology is validated by monitoring the displacements of a full-scale 6-story mass timber building during a series of shake table tests. Reasonable accuracy is achieved in that the overall root-mean-square errors of the tracking results are at the millimeter level compared to ground truth measurements from analog sensors. Insights on optimal features for monitoring structural dynamic response are discussed based on statistical analysis of the error characteristics for the various reference target patterns used to track the structural displacements. 

Incremental development is the process of writing a small snippet of code and testing it before moving on. For students in introductory programming courses, the value of incremental development is especially higher as they may suffer from more syntax errors, lack the proficiency to address complicated bugs, and may be more prone to frustration when struggling to correct code. However, to evaluate the effectiveness of interventions that aim to teach programming processes such as incremental development, we need to develop measures to assess such processes. In this paper, we present a way to measure incremental development. By qualitatively analyzing 15 student coding interviews, we identified common behaviors in the programming process that relate to incremental development. We then leveraged a dataset of over 1000 development sessions -- about 52,000 code snapshots at compilation time -- to automatically detect the common behaviors identified in our qualitative analysis. Finally, we crafted a formal metric, called the ``Measure of Incremental Development’' (MID), to quantify how effectively a student used incremental development during a programming session. The MID detects common non-incremental development patterns such as excessive debugging after large additions of code to automatically assess a sequence of snapshots. The MID aligns with human evaluations of incrementality with over 80% accuracy. Our metric enables new research directions and interventions focused on improving students' development practices.