By Michael Brenneis
With budgets that tend to favor new construction, many DOTs are finding it necessary to prioritize the most urgent repairs. But infrastructure decay is not always easily visible. And deferred or inadequate maintenance may occasionally have catastrophic consequences for U.S. bridges, 40 percent of which are at least 50 years old, and 9.1 percent of which are considered structurally deficient. A new remote sensing methodology may make the job of decay detection easier, and possibly more accurate.
A team of researchers, led by NASA’s Jet Propulsion Laboratory, have developed a technique to apply statistical modeling to synthetic aperture radar (SAR) satellite data, effectively increasing its resolution from meters to millimeters. This method of remote sensing can be used to quantify the decay of bridges and other infrastructure well beyond what can be observed from the ground by the unaided eye. Only infrastructure that has been systematically observed over a period of years using SAR can be analyzed in this way.
The researchers applied this technique to several years of SAR observations of the Morandi Bridge in Genoa, Italy—a bridge that collapsed unexpectedly on August 14, 2018, killing 43 people—and determined that their technique, had it been available, could potentially have forewarned of the collapse. The modeling technique showed increased movement of bridge components beginning in 2015, and more dramatic movement between March of 2017 and August of 2018.
The SAR measurement record approaches real time as satellites revisit their coverage areas every few days. A planned 2022 launch of another SAR-equipped satellite stands to further increase coverage. This new SAR analysis tool may soon be used in a practical way to inform the maintenance of critical infrastructure and help prioritize that which requires immediate attention.
Michael Brenneis is an Associate Researcher at SSTI.