Many of the questions Aspect’s infrastructure staff have on a project revolve around soil movement. We may need to know how much a building’s foundation has settled, or if a steep slope is starting to fail, or the furthest extent of a sinkhole. A new technology— interferometric synthetic aperture radar (InSAR)—is helping us gather better information to answer those questions. Project Geologist Annaliese Eipert will share Aspect’s local experience with InSAR at the monthly Association of Environmental & Engineering Geologists (AEG) meeting in Seattle on Thursday, March 17.
InSAR measures the changes in ground surface elevation by recording the distance between the ground and a satellite over time, and it does so with accuracy down to the millimeter. It can pierce through rainclouds and cover of night to document conditions without interruption. Unlike Global Positioning System (GPS) technology, which covers conditions for a fixed point, InSAR can collect data on the movement of large parcels of land. It also acts as a time machine of sorts, with the ability to study data gathered in years past. InSAR’s functionality gives us more detailed data to find problematic changes in ground surface and formulate appropriate recommendations and solutions.
InSAR image showing accumulated ground motion in the greater Tacoma area. Image courtesy of TRE-Altamira.
Annaliese’s presentation will focus on how we used InSAR data to help determine the cause of an approximately five-mile-long swath of widespread apparent uplift on the order of one inch in the Federal Way area that was observed between 2007 and 2009. She will also explore the potential causes of observed subsidence along Puget Lowland river valleys and of ground surface deformation in general, as well as the applications and limitations of using InSAR analysis for geologic and geotechnical engineering investigations in comparison to high-resolution GPS and Light Detection and Ranging (LiDAR) technology.
Annaliese will be co-presenting with Giacomo Falorni from TRE-Altamira, a globally recognized firm with comprehensive expertise in applying InSAR data to large infrastructure projects. Giacomo will provide an introduction to the technology itself and discuss how it has been used on infrastructure and environmental projects around the world.