Spring '13 Earth Science Thursday Speaker Series: Towards a pixel-by-pixel view of North America's changing surface using geodetic imaging
Thursday, April 25, 2013
to 5:00 PM
100 Keith-Wiess Geological Laboratories
6100 Main St
Houston, Texas, USA
For centuries, measurement of the shape of the Earth (called the science of geodesy) was necessarily time consuming. Even with new technologies like the Global Positioning System (GPS), vast portions of the Earth remain infrequently monitored for movement. Recently, a new form of geodesy has rapidly developed whereby image pairs can be compared to infer movements of the Earth's surface. Called geodetic imaging, the synoptic aircraft or satellite views allow large regions to be surveyed densely without any human setting foot in the area. Imaging geodesy encompasses several different types of methods including Interferometric Synthetic Aperture Radar (InSAR) as well as the automated comparison of SAR and optical images via pixel tracking. InSAR can image sub-centimeter deformation of the Earth's surface every 1-20 meters over areas spanning hundreds to thousands of kilometers. Pixel tracking is a very complementary tool to InSAR-- although the sensitivity to deformation is less (decimeter instead of sub-centimeter in a given image pair) and the horizontal spacing is coarser, it can be applied to both radar and optical images and often works when InSAR does not – for example, in areas that have large displacements or changes to the radar scattering properties of the ground. InSAR has allowed vast areas of the Earth's surface to be monitored frequently for deformation for the first time and this presentation will highlight some of the discoveries in North America and elsewhere, ranging from tectonics, magmatic processes, glaciers, groundwater, changes in vegetation, and human-induced ground deformation. A US InSAR mission was part of the original Earthscope plan. While the US InSAR mission (currently called DESDyni-R) is not likely to launch until 2019, Earthscope (along with NASA and others) has facilitated access to InSAR data over North America from several foreign satellite missions from 1992-present. There will soon be more than 300 Terabytes of raw SAR imagery available through UNAVCO and the Alaska Satellite Facility (more than the available . Most of this data is from the Japanese ALOS mission which had a radar wavelength of 23 cm that is capable of making coherent interferograms over most of North America for the first time. This presentation will discuss how to get access to that data, how to set up a processing capability, and what types of problems this data can and cannot be used to address.
Biography of Matthew Pritchard: http://www.geo.cornell.edu/eas/PeoplePlaces/Faculty/matt/Pritchard.html/