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My research group worked on high-precision GPS applications, mostly for geoscientists. I began using GPS to measure crustal deformation in southern California.  After I received my PhD, I continued working on plate boundary deformation, but also started thinking about measuring global effects with GPS:  plate tectonics, effects of ice mass changes, and glacial isostatic adjustment. In the late 1990s and early 2000s, I moved on to bigger signals: moving ice sheets, volcanoes, and earthquakes. All of these signals required that we develop new ways of analyzing GPS data. There was also a several year diversion into timing and relativity effects where I worked with researchers at NIST. For many years I also worked on episodic slip and tremor in Guerrero, Mexico with geoscientists at UNAM. About 15 years ago I began trying to model and remove multipath effects, mostly to improve GPS records of seismic displacements. It was that effort that led to my group’s work on GPS reflections. We use these data to study near-surface soil moisture, vegetation water content, snow depth, water levels, and permafrost signals. A special effort focused on developing water cycle products from EarthScope data: PBO H2O. I am now retired from CU, but I am still interested in new ways of looking at GPS (and GNSS) data.  I recently made a web app.