Filling in Where UAS Cannot: Using Comprehensive Scanning Setups
Improving and Applying our Imaging Systems
The adaptation of UAS imaging and 3D data acquisition has proven to be a monumental benefactor for the civil industry. According to AASHTO, UAS use in state DOTs has increased to 72% in 2019, and a likely 100% this year of 2021. While not all these applications are inspection-based, that's nearly double the use observed in 2017. The implications in the increase in inspector safety are now proven beyond reasonable doubt and the sheer amount of data which can.
NEXCO has worked with its NDE partners to combine and supplement imaging and laser scanning datasets taken by drones. For example, we worked with a construction company to image box girder interiors and exteriors of a complex bridge. This project produced detailed deliverable sets that mapped deficiencies both minor and major. Through this experience and several others, however, we came to understand the current limitations of this powerful technology. To fill in where UAS could not, we have successfully applied our stationary and semi-mobile imaging system, U3S.
There are two notable drawbacks that drones still demonstrate in a structural inspection setting: 1) payload limitation/fall risk, and 2) resolution of imagery gathered. Regarding the first point, some sensor equipment is simply too heavy and expensive to hoist several hundred feet in the air. Cooled infrared cameras are a perfect example to illustrate this point: they cost upwards of $50,000, so dropping them is not a risk most vendors are willing to take. The class of drones needed to hold these types of cameras can also get expensive, given that the equipment needed to run these cameras can easily exceed 15lbs.
Regarding the second point, in nearly all capturing environments our team has come across so far, visual imaging resolution has trouble surpassing the resolution needed to conduct prestressed concrete crack inspections and infrared scanning in certain environments. The level of resolution required is less than 0.3mm for insignificant crack detection and greater than 0.3mm for moderate (AASHTO Element Level Inspection Guide). Most drone imaging result max out at 1mm width detection, provided wind conditions to not blur images through flightpath disruption. Infrared resolution is also important for bridge element inspection, since the detection of minute temperature differentials is critical for accurately mapping subsurface delamination.
In conclusion, we emphasize that drone applications are a powerful asset for overview evaluations and special access locations. To fill in for applications that require precision imaging, however, our U3S platform can provide the accuracy in deficiency detection and stitching of imagery needed for comprehensive inspection projects.
NEXCO-West USA Celebrates its 10th Anniversary
This month, NEXCO celebrated its 10th Anniversary. An online reception was held on 1/11 and we welcomed a few hundred attendees, several of which shared their thoughts and kind messages of appreciation.
Our president and CEO, Masato Matsumoto, reviewed notable projects over the past 10 years, including our signature network-level bridge deck scanning efforts in Virginia, Indiana, Pennsylvania, and Florida. He also covered our 21-mile scan of tunnel liner for the Washington Metro, our comprehensive imaging of the Pearl Harbor Memorial bridge in Connecticut, among other notable successes.
For those who attended the reception, please accept our deepest gratitude. We will continue to show our unwavering resolve in providing the best imaging services on the market in the coming years.