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GIS: A New Profession? 总被引：1，自引：0，他引：1
Nancy J. Obermeyer 《The Professional geographer》1994,46(4):498-503
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Refraction effects of optical beams are generally caused by an inhomogeneous propagation medium and are a major source of systematic errors in the precise optical determination of angles and distances in the atmospheric surface layer. In this contribution a method for deriving vertical temperature and refractive index gradients from optical scintillation is presented. Knowledge of these gradients is required for the compensation of atmospherically induced errors for highly precise terrestrial geodetic measurements, like direct transfer and levelling. The advantage of the present optical method is, that temperature and refractive index gradients can be derived as line-averaged values over the propagation path, which is not possible by meteorological point measurements. Field observations have been carried out with a displaced-beam scintillometer over flat terrain and under different atmospheric conditions in order to verify this method. The experiments show, that this method allows to derive accurate correction values for precise terrestrial geodetic measurements. 相似文献
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Natural electromagnetic radiation (EMR) and its application in structural geology and neotectonics 总被引：2，自引：0，他引：2
Reinhard O. Greiling Hennes Obermeyer 《Journal of the Geological Society of India》2010,75(1):278-288
Natural electromagnetic radiation (EMR) impulses are emitted from rocks under stress. Electromagnetic emission may start during
crystal deformation prior to and during the nucleation phase of nanocracks. The emission direction is either parallel with
or normal to the crack surfaces. The EMR magnetic component is measured by the sensor or aerial of an instrument, the Cerescope,
at frequencies from 5 to 50 kHz. Measurements at the surface show directions of recent stresses remarkably well. A calibration
of EMR intensity in terms of stress magnitude is possible in tunnels, where the overburden pressure can be calculated. Two
examples from the Upper Rhine Graben and NW India show EMR line measurements. In both cases, stress concentrations at fault
or bedding surfaces can be detected. These surfaces can be regarded as tectonically active. Two further examples of EMR determinations
in tunnels give more detailed information on the regional stress field. The example from the Swiss Jura fold-and-thrust belt
shows directional results, with different directions beneath and above the regional detachment horizon at the base of the
belt. The example from central Scandinavia shows a late Caledonian shear zone as a boundary between two recent stress domains,
and gives absolute values of stress. 相似文献
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