Long-Term Use of Automated Total Station to Monitor Movement of High-Rise Buildings in New York City

Described in this paper is the use of an Automated Motorized Total Station (AMTS) for 18 months to monitor potential movement of buildings around a deep excavation in rock. The approximately 24.4-meter deep excavation is for a new high-rise building located in Manhattan. The AMTS was installed on top of an adjacent building in the vicinity of the excavation, with four mini-prisms acting as backsights. More than 30 mini-prisms (targets) were installed, in a few rows, on three buildings abutting the excavation. The AMTS was set up to read distance, azimuth (bearing of line-of-sight), and angle from the horizontal (of the line-of-sight), each hour for the duration (18 months) of the excavation and building construction to street level. The data that we have collected include: target coordinates — calculated by a proprietary software — based on measurements of the AMTS, temperature at AMTS location for a few weeks, distance from AMTS to the targets, our estimate of potential movement of the buildings involved due to periodic change in temperature, and accuracy of AMTS in distance and angle measurements as reported by the manufacturer. A summary of the most likely magnitude of errors, which contribute to the calculated coordinates of survey targets, and partial details of the closed-form solution, will be presented. Recommendations for future research are also provided.