The effects on cost, time, and accuracy when using unmanned aircraft systems to measure sloped excavations

Abstract

As uses for unmanned aircraft systems (UAS) continue to evolve, opportunities for research to validate improvements in cost, time, and quality become crucial. Specifically, there have been many studies focused on how UASs can simplify the measurement of earthwork quantities, but is there a compromise in the accuracy of the measurements for a reduced effort to obtain them? The objective of this research was to identify if such a compromise exists. This study measured the amount of effort (cost and time) to obtain a level of accuracy (quality) that is consistent with the traditional measurements obtained with ground-based robotic surveying equipment. The researchers performed a quantitative experiment using twelve measurement check points across a one-acre test site (4,047 m2). The test site was sloped to simulate a level of complexity that would be consistent with a more challenging area of a typical construction project site when obtaining earthwork quantities. The methodology involved measuring three separate UAS flights with differing flight paths and image gathering overlaps and comparing this to a ground-based measurement procedure. An accuracy analysis was conducted on the location of the twelve check points. Time and cost data were computed for all procedures and compared. This study found that not all flight path techniques met industry standards for accuracy while others did. The tradeoff when using the more accurate flight paths was a longer time to obtain and process data. When the overall cost was considered, it was determined that the UAS-based measurement approach was less expensive – resulting in a mixed determination about whether a “compromise” existed. This study further elaborates on the findings and proposes recommendations about how this comparison benefits innovation in the built environment.