Accounting for Galileo–GPS inter-system biases in precise satellite positioning     

Jacek Paziewski  Pawel Wielgosz 《Journal of Geodesy》2015,89(1):81-93

  相似文献   

The Shallow Weathered Fracture Layer in the Near–Stream Zone     

W. J. Gburek  J. B. Urban 《Ground water》1990,28(6):875-883

  相似文献   

Correlation of Plio-Pleistocene deposits of the Lower Rhine Basin (North-West Germany) and the Valle Ricca pits (Central Italy)     

Claudio Arias  Giulio Bigazzi  Francescopaolo Bonadonna  Karl Brunnacker  Brigitte Urban 《Quaternary Science Reviews》1984,3(1):73-89

Biostratigraphic and palaeomagnetic research has been carried out on selected profiles in North-Western Germany and Central Italy in order to correlate Plio-Pleistocene sections.Around the Réunion subchronozone, vegetation in the Valle Ricca was dominated by a mountain forest type pointing to cool climatic conditions. In the Lower Rhine Basin vegetation had a slightly warmer character, but was also dominated strongly by a mountain type of forest vegetation, characteristic of cooler summers and higher precipitation than at present.Two warmer periods have been determined in the Central Italian profiles; the youngest around the Olduvai reversal, should correspond to the youngest Tiglian beds of the Lower Rhine Basin.Deposits older than the Réunion subzone have not been found in the Valle Ricca. In the Lower Rhine Basin, on the other hand, the Gauss-Matuyama boundary is located between the uppermost Pliocene, the Reuverian C and the Praetiglian.  相似文献   

Selection criteria for continuous channel electron multipliers in space applications     

A. Urban 《Astrophysics and Space Science》1982,83(1-2):3-14

Criteria for selecting continuous channel electron multipliers were applied to fifteen Mullard units without significantly affecting their overall lifetime. The gain fatigue vs accumulated counts, the change of the pulse height distribution during lifetime, the gain degradation vs count rates as well as the gain vs operating voltage and the resolution vs operating voltage have been investigated using a tritium source. The results provide several criteria to determine good, marginal and poor multipliers. From all tested devices 25% had a very low gain and did not operate satisfactory at the end of their lifetime investigations (4×10⁹ accumulated counts). 40% of all devices could be classified as good multipliers. Their main characteristic was a gain recovery phenomenon after 3×10⁹ accumulated counts with a progressive gain stabilizing. Multipliers classified as marginal exhibited some unexpected behaviour during the lifetime but a gain recovery phase and gain plateau region could be identified. Furthermore, the relative efficiency of the multipliers vs electron energy as a function of the operating voltage has been measured by using a near monoenergetic electron beam.Originally submitted to the journalSpace Science Instrumentation.  相似文献   

Transboundary impacts on regional ground water modeling in Texas   总被引：1，自引：0，他引：1  

Rainwater K  Stovall J  Frailey S  Urban L 《Ground water》2005,43(5):706-716

Recent legislation required regional grassroots water resources planning across the entire state of Texas. The Texas Water Development Board (TWDB), the state's primary water resource planning agency, divided the state into 16 planning regions. Each planning group developed plans to manage both ground water and surface water sources and to meet future demands of various combinations of domestic, agricultural, municipal, and industrial water consumers. This presentation describes the challenges in developing a ground water model for the Llano Estacado Regional Water Planning Group (LERWPG), whose region includes 21 counties in the Southern High Plains of Texas. While surface water is supplied to several cities in this region, the vast majority of the regional water use comes from the High Plains aquifer system, often locally referred to as the Ogallala Aquifer. Over 95% of the ground water demand is for irrigated agriculture. The LERWPG had to predict the impact of future TWDB-projected water demands, as provided by the TWDB, on the aquifer for the period 2000 to 2050. If detrimental impacts were noted, alternative management strategies must be proposed. While much effort was spent on evaluating the current status of the ground water reserves, an appropriate numerical model of the aquifer system was necessary to demonstrate future impacts of the predicted withdrawals as well as the effects of the alternative strategies. The modeling effort was completed in the summer of 2000. This presentation concentrates on the political, scientific, and nontechnical issues in this planning process that complicated the modeling effort. Uncertainties in data, most significantly in distribution and intensity of recharge and withdrawals, significantly impacted the calibration and predictive modeling efforts. Four predictive scenarios, including baseline projections, recurrence of the drought of record, precipitation enhancement, and reduced irrigation demand, were simulated to identify counties at risk of low final ground water storage volume or low levels of satisfied demand by 2050.  相似文献   

On the reliability of the VCV Matrix: A case study based on GAMIT and Bernese GPS Software   总被引：1，自引：0，他引：1  

Israel?KashaniEmail author  Pawel?Wielgosz  Dorota?A.?Grejner-Brzezinska 《GPS Solutions》2004,8(4):193-199

Commonly, the variance-covariance (VCV) matrix derived from GPS processing software underestimates the magnitude of the error, mainly due to the fact that physical correlations are normally neglected. The GAMIT and Bernese software packages serve the scientific community as important tools for GPS measurement processing and analyzing, especially in precise applications. Therefore, the reliability of the VCV matrices derived by the GAMIT and Bernese packages is of great importance. Formal accuracies derived from both software need to be scaled by applying a scaling factor (SF) that multiplies the software-derived formal errors. However, to the best of our knowledge, no standard approach approved by the GPS community exists. In this report, an analysis is carried out in order to test the reliability and the validity of the VCV matrices in both software, and to provide SFs needed to calculate the realistic accuracies reflecting the actual error levels. The method applied in this study allows deriving SFs for formal accuracies obtained from GAMIT and Bernese. The results attained from the time series of eight days for eight baselines (lengths of 20–415 km) indicate that the overall SF for GAMIT is more than 10 times smaller than for Bernese (1.9 and 23.0, respectively). Although no distance-dependent SF was detected in either case, the session-duration dependence was detected for the Bernese software, while no clear session-duration dependence was observed for the GAMIT. Furthermore, no receiver/antenna dependence could be deduced from the results of this analysis.  相似文献   

Violations of Gutenberg–Richter Relation in Anthropogenic Seismicity     

Pawel Urban  Stanislaw Lasocki  Patrick Blascheck  Aderson Farias do Nascimento  Nguyen Van Giang  Grzegorz Kwiatek 《Pure and Applied Geophysics》2016,173(5):1517-1537

  相似文献   

An automated 3D modeling of topological indoor navigation network     

Ali Jamali  Alias Abdul Rahman  Pawel Boguslawski  Pankaj Kumar  Christopher M. Gold 《GeoJournal》2017,82(1):157-170

Indoor navigation is important for various applications such as disaster management, building modeling, safety analysis etc. In the last decade, indoor environment has been a focus of wide research that includes development of indoor data acquisition techniques, 3D data modeling and indoor navigation. In this research, an automated method for 3D modeling of indoor navigation network has been presented. 3D indoor navigation modeling requires a valid 3D model that can be represented as a cell complex: a model without any gap or intersection such that two cells (e.g. room, corridor) perfectly touch each other. This research investigates an automated method for 3D modeling of indoor navigation network using a geometrical model of indoor building environment. In order to reduce time and cost of surveying process, Trimble LaserAce 1000 laser rangefinder was used to acquire indoor building data which led to the acquisition of an inaccurate geometry of building. The connection between surveying benchmarks was established using Delaunay triangulation. Dijkstra algorithm was used to find shortest path in between building floors. The modeling results were evaluated against an accurate geometry of indoor building environment which was acquired using highly-accurate Trimble M3 total station. This research intends to investigate and propose a novel method of topological navigation network modeling with a less accurate geometrical model to overcome the need of required an accurate geometrical model. To control the uncertainty of the calibration and of the reconstruction of the building from the measurements, interval analysis and homotopy continuation will be investigated in the near future.  相似文献   

Spatial organization of seismicity and fracture pattern in NE Italy and W Slovenia     

G.?Bressan  M.?Ponton  G.?RossiEmail author  S.?Urban 《Journal of Seismology》2016,20(2):511-534

The study focuses on the spatial organization of seismicity and the relation between fracture pattern and earthquakes in the Friuli (north-eastern Italy) and western Slovenia seismic regions. The structural setting is characterized by a complex structure resulting from the superposition of several tectonic phases that generated NW-SE trending Dinaric faults and about E-W trending Alpine faults. The upper crust is characterized by lithological and mechanical heterogeneities. The fractal analysis shows that, in general, the seismicity only partially fills a plane. Only in a few cases, the earthquakes distribute on planar structures. The orientation of planes that fit through the hypocentres shows a different disposition at the two depth intervals analysed. The shallower interval (0–10 km) is characterized by planes with highly variable orientations. The spatial seismicity is investigated in the context of a general damage model, represented by the crack density distribution. The results evidence that the seismicity appears mostly located along sharp transition areas from low crack density to higher crack density, i.e., from zones of low damage to zones of intermediate damage. These zones are characterized by high heterogeneity due to the superposition of different tectonic phases and by the maximum interference between Dinaric and Alpine domains. The orientation of the planes fitting the seismicity at 10–20-km depth appears less dispersed, coinciding with the trend of Dinaric sub-vertical faults in the northern and eastern parts of the study area, and with Alpine low-angle faults in the western and southern parts.  相似文献   

Quality assessment of GPS rapid static positioning with weighted ionospheric parameters in generalized least squares   总被引：3，自引：2，他引：1  

Pawel Wielgosz 《GPS Solutions》2011,15(2):89-99

Precise GPS positioning requires the processing of carrier-phase observations and fixing integer ambiguities. With increasing distance between receivers, ambiguity fixing becomes more difficult because ionospheric and tropospheric effects do not cancel sufficiently in double differencing. A popular procedure in static positioning is to increase the length of the observing session and/or to apply atmospheric (ionospheric) models and corrections. We investigate the methodology for GPS rapid static positioning that requires just a few minutes of dual-frequency GPS observations for medium-length baselines. Ionospheric corrections are not required, but the ionospheric delays are treated as pseudo-observations having a priori values and respective weights. The tropospheric delays are reduced by using well-established troposphere models, and satellite orbital and clock errors are eliminated by using IGS rapid products. Several numerical tests based on actual GPS data are presented. It is shown that the proposed methodology is suitable for rapid static positioning within 50–70 km from the closest reference network station and that centimeter-level precision in positioning is feasible when using just 1 min of dual-frequency GPS data.  相似文献