Monitoring Earth Surface Dynamics with Optical Imagery
<p>Despite the increasing availability of high-quality optical satellite images, continuous monitoring of Earth's surface changes is still of limited use due to technical limitations. To overcome these limitations, this thesis presents a processing chain to accurately orthorectify and co-...
| Summary: | <p>Despite the increasing availability of high-quality optical satellite images, continuous monitoring of Earth's surface changes is still of limited use due to technical limitations. To overcome these limitations, this thesis presents a processing chain to accurately orthorectify and co-register sets of satellite and aerial images, which, associated with a precise correlation technique, allow for the measurement of horizontal ground deformations with accuracy better than 1/10 of the pixel size. The irregular resampling problem is addressed to avoid introducing aliasing in the orthorectified images. Image registration and correlation is achieved with an iterative, unbiased processor that estimates the phase plane in the Fourier domain for sub-pixel shift detection. Errors due to the imaging system are calibrated and modeled, topography artifacts are characterized and solutions are proposed to compensate or to filter them.</p>
<p>A software package implementing these procedures, Co-registration of Optically Sensed Images and Correlation (COSI-Corr), is available from the Caltech Tectonics Observatory website. The procedure is validated in several different contexts, and applied to seismo-tectonics and glaciology studies.</p>
<p>Accurate measurements of horizontal co-seismic displacements in the near fault zone allow unambiguous imaging of surface ruptures. It is shown that measurements of surface ruptures from optical aerial and satellite images compare well with field measurements, and that in addition they have the potential of densely measuring the fault perpendicular component, and the off-fault distributed slip. When combined with seismic waveform modeling, fault geometry and surface offsets add crucial constraints to describe in details the seismic faulting process.</p>
<p>Dense maps of glacier velocity are reported for several glaciers in Europe and in the Himalayas. Optical image correlation proves robust even in challenging mountainous areas, allowing accurate measurements of glacier flow velocity. Seasonal variations of glacier flow velocity are well identified, suggesting that such measurements can be used to better study the effects of climate change, and to refine the tuning of numerical glacier models.</p> |
|---|