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Carbon dioxide (CO2) transfer from inland waters to the atmosphere, known as CO2 evasion, is a component of the global carbon cycle. Global estimates of CO2 evasion have been hampered, however, by the lack of a framework for estimating the inland water surface area and gas transfer velocity and by the absence of a global CO2 database. Here we report(More)
The Shuttle Radar Topography Mission (SRTM) produced near-global 1Љ and 3Љ DEMs. The cartographically-derived National Elevation Dataset (NED) provides a mechanism to assess SRTM quality. We compared 12 geomorphometric parameters from SRTM to NED for about 500,000 sample areas over the continental United States. For basic parameters like average elevation(More)
Digital elevation models (DEMs) cover a wide range of scales, and allow statisticalanalysis of geomorphometric parameters. At global or continental scale, DEMs covering rectangular quadrangles can be considered random samples. Average quadrangle values can be compared at different DEM scales, and for different physiographic provinces. Three independent(More)
—Recent advances in computer technology herald a revolution in geomorphometry. Desktop computers and 64 bit operating systems can access massive data sets like the entire SRTM DEM from RAM. Multi-temporal lidar topography, with 1 m or 0.5 m grid spacing, can require gigabytes of data for relatively small project areas, but repeated surveys allow monitoring(More)
The ASTER GDEM purports to be the highest resolution global digital elevation model, with 30 m spacings (actually 1 arc second). We have compared the GDEM with SRTM 3 arc second data for 52 locations in Europe and North America, using NextMap IFSAR DSM and DTM pairs for absolute calibration. In addition, for the 6 North American sites we have also compared(More)
Intervisibility computed from a lidar point cloud offers several advantages compared to using a gridded digital surface model: (1) even with high resolution grids, the point cloud offers a better graphical depiction of the line-of-sight, and (2) the point cloud avoids interpolation problems that frequently result in the grid not accurately capturing the(More)