Formalization of workflows for extracting bridge surveying goals from laser-scanned data

Laser scanners enable bridge inspectors to collect dense 3D point clouds, which capture detailed geometries of bridges. While these data sets contain rich geometric information, they bring unique challenges related to geometric information retrieval. This paper describes a case study to show the necessity and potential value of automating the manual data processing workflows being executed for extracting geometric data items (surveying goals) from 3D point clouds, and presents an approach for formalizing these workflows to enable such automation. We analyzed manual procedures of taking measurements on 3D point clouds and as-built models for obtaining bridge inspection related surveying goals, synthesized and categorized all data processing operations into nine generic operations. These nine categories of operations can be formalized using < operator, inputs, output, parameters, constraints> tuples. Using these tuples, we formalized an operation library and workflow construction mechanisms for enabling inspectors to semi-automatically construct executable workflows. This formalism also incorporates several mechanisms for facilitating extensions to the existing operation library to accommodate additional surveying goals that have not been covered. The developed approach is validated for its generality to support workflows needed for all surveying goals required by the National Bridge Inventory (NBI) program, and for its extensibility to support workflows needed to support a variety of other surveying goals identified in the Architecture/Engineering/Construction domain.