Lateral and subsidence movement estimation using InSAR

Ground movement poses a hazard to buried infrastructure (e.g., pipelines) as either massive instantaneous movement leading to serious failures or as small incremental movement over a period of time resulting in catastrophe, are common. Conventional ground motion detection and measurement techniques require regular costly surveys and operational cost increase in geographically dispersed areas. The measurement of ground movement (e.g., subsidence) using DInSAR (Differential Interferometric Synthetic Aperture Radar) is a well established technique and many studies have been completed to validate its performance. In these studies, ground movement is generally derived from a single look direction (e.g., subsidence only). Strictly speaking, if one look direction is used to obtain ground movement estimates, then only one dimension of movement can be derived. This can produce significant errors in measuring subsidence, especially in the case of localized movement producing significant lateral movement. This work discusses a technique for extracting lateral ground displacement using interferometry and a data fusion, least squares estimation technique from multiple SAR look directions. It is shown that meaningful three dimensional movement estimates can be derived within expected sensor error, with a dramatic reduction in errors of subsidence measurements over a single look direction measurement. The validation was accomplished using a time series of satellite data collected over a pipeline right of way in 2001, along with a series of traditional surveys for comparison.