Dating of paleolakes in the central altiplano of bolivia English girls xnxx


20-Nov-2014 01:23

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We fit corrected GPS trajectories with 2-D Fourier basis functions, from which we created a digital elevation model (DEM) of the surface whose absolute accuracy we estimate to be at least 2.2 cm RMSE.With over two magnitudes better vertical resolution than the Shuttle Radar Topography Mission data, this DEM reveals decimetre-level topography that is completely absent in other topographic data sets.Although the current dry period has persisted for at least 8000 yr (Sylvestre 1999), hydrological activity continues in the form of periodic flooding which regenerates the surface via the dissolution and redeposition of salt (Lowenstein & Hardie 1985) and appears to be responsible for maintaining the salar's extraordinary smoothness.As an extremely broad and flat terrestrial surface, the salar de Uyuni is an ideal reference target for Earth-orbiting altimeters. We report on a kinematic Global Positioning System (GPS) survey of a 45-by-54 km area in the eastern salar, conducted in September 2002 to provide ground truth for the Ice Cloud and land Elevation Satellite (ICESat) mission.GPS post-processing included corrections for long-period GPS noise that significantly improved survey accuracy.Radar altimeters such as Envisat and TOPEX/Poseidon (e.g.Fu 1994) and the laser altimeter aboard NASA's Ice Cloud and land Elevation Satellite (ICESat) (Schutz 2005) can measure the elevation of flat surfaces to within 5 cm rms, which is two orders of magnitude better than the 6.2 m (90 per cent confidence level) accuracy of Shuttle Radar Topography Mission (SRTM) over South America (Rodriguez 2005).

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expanse of halite at 4 km above sea level in the Andean Altiplano.The motivation for this paper was a kinematic Global Positioning System (GPS) survey of the salar de Uyuni carried out in September 2002 to provide ground truth for the ICESat laser altimeter (see Fricker 2005).The salar is the lowest point of an internal drainage basin that has undergone many cycles of inundation and evaporation throughout the late Quaternary (Argollo & Mourguiart 2000; Fornari 2000).Interlayered salt and mud deposits reaching depths of hundreds of metres in the centre of the salar (Baker 2001; Fritz 2004) are relics of a long history of sedimentation during lacustrine phases followed by the deposition of halite in the lower reaches of the basin when the lakes retreated and evaporated (Risacher & Fritz 2000).

Each overflight of the salar can yield hundreds of altimeter ground returns whose waveforms are unmodified by topography and whose reported elevations vary minimally across the surface.Validation of altimeter measurements requires far better vertical resolution than is provided by existing topographic data sets, however.