Geomorphology From Earth Orbit - Can it be Done?

High spatial and spectral resolution electromagnetic imaging data from orbit is now routinely used within a variety of earth science disciplines, including geomorphology, to assess the effects and state of dynamic earth surface processes, as well as for basic geological and geographical mapping. Temporal sampling ranges from very frequent (e.g., multiple times per week for MODIS) at coarse spatial scales (e.g., 250m to 1km/pixel) to relatively infrequent (e.g., a few times per year for ASTER, or worse considering cloud cover constraints) at geomorphically very useful spatial scales (e.g., <100m/pixel). Observations include spectrophotometric optical image data at visible and near to mid-infrared wavelengths, precise ground temperature and emissivity observations in thermal infrared bands, and topography measurements using optical and microwave data, the latter typically being among the most directly useful geomorphic observations. While such data are helpful in addressing a variety of basic and applied science problems, including issues related to geologic hazards, and are capable of providing a regional to global context, (e.g., ala Victor Baker's "mega-geomorphology" in Short and Blair, 1986, NASA SP-486) a potential question remains vis-à-vis traditional field techniques, as to whether remote sensing data are ever both necessary and sufficient to completely characterize a problem or whether correlative in situ data are a fundamental requirement to completely specify problems of interest. More likely, the necessary balance between the two is idiosyncratic with respect to any individual problem, especially when considering the range of geomorphic arenas being considered (e.g., volcanology, glacial and periglacial processes, hydrology and fluvial geomorphology, mass wasting, coastal studies, eolian studies, and geomorphology related to climate change). We will explore the strengths and weaknesses of emerging remote sensing techniques and practice with respect to scale, sampling frequency, available spectral ranges, accuracy and precision, and requirements for correlative in situ ground truth, in the geomorphic context. (This work was carried out in part at the Jet Propulsion Laboratory of the California Institute of Technology under contract to NASA.)