Invitation

by Melany Bohm (GFZ)

When: Thursday, May 11, 2017 Time: 14.00 p.m.

Where: Buliding H, Lecture Hall

GPS Can't Do That, Can It?

Kristine M. Larson 
(Department of Aerospace Engineering Sciences University of Colorado, Boulder Alexander von Humboldt Research Awardee and visiting scientist at the GFZ in section Space Geodetic Techniques)

will give a talk on

"How working on GPS seismology led to the development of a GPS snow, soil moisture, vegetation, and water level sensor"

Date: Thursday, May 11, 2017 Time: 14.00 p.m.
Place: Buliding H, Lecture Hall

About 15 years ago I began working on developing methods so that GPS could be used to measure ground displacements during large earthquakes. At the time, almost all geodesists estimated station positions once per day, as this is entirely adequate for tectonic applications. Standard geodetic analysis tools (then and now) ignore the error caused by signals that reflect off the land surface. My group quickly realized that surface reflections were the largest error source in GPS seismology and developed tools to mitigate their impact. That early work in GPS seismology ultimately led us to new work in hydrogeodesy - where reflected GPS signals are used to turn a GPS antenna into a bi-static radar. The reflected GPS signals can be used to measure surface soil moisture, snow depth, water levels and vegetation water content. We have been able to take advantage of the recently installed Plate Boundary Observatory (PBO) to apply these methods on a large scale; we call this initiative PBO H2O (http://xenon.colorado.edu/portal).

In this talk I will provide some background on GPS for tectonic and seismic applications, explain how GPS interferometry works, and then show water cycle products derived from GPS data. I will also share some new work I’ve been doing using GPS data to: detect ash in volcanic plumes and estimate firn density on ice sheets in Greenland and Antarctica.