aerial perspective - Photogrammetry: An Oregon bridge project shows that this survey approach reduces risk, cost, and traffic delays

摘要

When engineer Laura Schmidt arrived at her dollar10 million bridge replacement project site, the surveyors were just beginning to lay out the stakes for the roadway approaches to the bridge and the contractor was finalizing construction of the bridge deck and preparing for construction of the roadway approaches. However, as soon as Laura got out of her car, her survey party chief abruptly stalked toward her, his face pale and grim with obvious worry. Before she could ask him what was going on, he uttered the last words any engineer wants to hear: "We have a problem." The party chief explained that the roadway approaches appeared to be six inches lower in reality than her design had anticipated. Her stomach fell as she considered the implications of this error. First, she would have to find a week's worth of time to revise her roadway specifications to reflect the actual conditions on the ground, as she had based her entire design on an inaccurate model produced by the survey crew. Next, Laura realized that because the roadway would need to be raised six inches, she would have to increase the quantity of roadway embankment fill materials. This would necessitate the costly process of preparing a change order and compensating the contractor for this large addition to his scope of work.