Accuracy and Geometric Decomposition

Lack of automatic support for data collection and interpretation makes the laser scanning based bridge geometric data acquisition process prohibitive to ordinary bridge inspectors. First, even though from the technical data of a laser scanner bridge inspectors can know how accurate each point can be positioned, what are more useful for them are the accuracy of geometric features which can be extracted from dense point cloud such as how much uncertainty lies in the normal values of an extracted plane. Evaluation of those geometric features and extraction of high level uncertainty information require bridge inspectors to know how to do manual uncertainty analysis. In addition, that process is too complicated for on-site data evaluation to get a quick feedback about the data quality. Second, bridge inspectors need to manually analyze the relationship between the accuracy of single geometric features and the value generated based on them. Interestingly, accuracy constraints for a group of geometric features can have multiple solutions to achieve the same accuracy level for their corresponding inspection goal. So if bridge inspector can get a tool to show them the trade-off between the accuracy constraints to achieve specific accuracy requirement for an inspection goal so that they can have more alternatives on site and get more flexibility on site. Third, bridge inspectors need to interpret accuracy into a series of surveying strategies such as locate the scanners within 10 m from the target object.