He is the author of over 226 refereed publications. Research interests include imaging spectrometry, remote sensing of vegetation, spectroscopy (urban and natural cover), land-use/land-cover change mapping, sensor fusion (including thermal), remote sensing of wildfire and trace gasses such as methane. He has worked extensively with passive optical sensors such as imaging spectrometry and active sensors, such as LiDAR. He is best known for developing the concept of Multiple Endmember Spectral Mixture Analysis (MESMA), and pioneering work in hyperspectral remote sensing, including mapping plant species. He is a Fellow of the American Geophysical Union.