InSAR Applications for Highway Transportation Projects

Satellite Synthetic aperture radar (SAR) technology, in combination with interferometry (InSAR), has the ability to measure topography or ground movement to sub-centimeter accuracy. Many factors affect the ability to apply InSAR for the detection of slope movement. If these factors are considered, InSAR can often be successfully used to monitor slope movement. The Federal Lands Highway Program (FLH) of the Federal Highway Administration (FHWA) has initiated the project described within this report to evaluate the utility of InSAR technology to monitor slide movements that impact road networks. The project objective was to establish and demonstrate reliable, cost effective procedures to measure ground movement using InSAR in support of federal highways projects. This report describes the effectiveness of InSAR in monitoring ground movement, and recommends guidelines for the coordinated use of InSAR with other FLH data collections, including photogrammetry, field surveys, boreholes and slope inclinometers. InSAR has the unique ability to measure both present and prior (based on the data archives accumulated over the last 12 years) ground movement and consequently, the present study involved collection and analysis of InSAR data from both the past and present at three sites. The first site, the Prosser slide in Benton County WA, provided a site with excellent InSAR coherence and gradual creeping movement that demonstrated the limits of InSAR movement measurement. The combination of a set of InSAR movement maps over a two-year period produced movement on the order of several centimeters that qualitatively correlated well with site observations and slope inclinometer measurements. The second slope, the Cimarron slide in Owl Creek CO, exhibited moderate coherence and highly visible InSAR movement signatures were produced over periods of only several months. The third site, in Mesa Verde National Park near Cortez, CO, is a region of significant topographic relief, which made the use of satellite-based InSAR a challenge.