269 resultados para Geodetic satellites


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The publication of the Law 10,267 of 08/28/2001 changed the paradigm of rural registration in Brazil, because this law known as the Law of Georeferencing has created the National Registration of Rural Property, that unifies in a common basis different registrations present in several government agencies, such as the National Institute for Colonization and Agrarian Reform (INCRA), the Secretariat of Federal Revenue, the Brazilian Institute of Environment and Natural Resources, and the National Indian Foundation. Also, this new registration system has a graphical component which has not existed until such date, where the boundaries of rural property are georeferenced to the Brazilian Geodetic System. This new paradigm has resulted in a standardization of the survey and its representation of rural properties according to the Technical Standard for Georeferencing of Rural Properties, published by INCRA in compliance with the new legislation. Due to the georeferencing, the creation of a public GIS of free access on the Internet was possible. Among the difficulties found it may be observed the great Brazilian territory, the need for specialized professionals, and especially the certification process that INCRA has to perform for each georeferenced property. It is hoped that this last difficulty is solved with the implementation of the Land Management System that will allow automated and online certification, making the process more transparent, agile and fast.

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Since 2000 the use of the GPS navigation increases considerably. The reason for that was the deactivation of the selective availability in May 2000. However, these receivers do not register the observables, they just estimate and store them and that prevents the post-processing data. Based in this aspect some softwares were developed and are available for free. They allow recording the GPS observables, pseudorange and carrier phase. These programs are able to read in binary files and record information concerning the GPS observables and to convert binary format to a RINEX format. This study presents the GPS Garmin 12 XL evaluation using free programs. Two experiments were carried out in Presidente Prudente-SP region using the relative static survey. The processing was carried out with intervals of 30, 15, 10 and 5 minutes. The results were compared with the coordinates from a geodetic receiver and show that 98.9 % of the points, the values in relation to the planimetric accuracy were better than 0.50 m. The only baseline which the value was larger or equal to 0.50 m is the point M0001 (baseline lesser than 2 km) referred to the first experiment. In terms of precision the values did not exceeded 0.30 m.

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Algae bloom is one of the major consequences of the eutrophication of aquatic systems, including algae capable of producing toxic substances. Among these are several species of cyanobacteria, also known as blue-green algae, that have the capacity to adapt themselves to changes in the water column. Thus, the horizontal distribution of cyanobacteria harmful algae blooms (CHABs) is essential, not only to the environment, but also for public health. The use of remote sensing techniques for mapping CHABs has been explored by means of bio-optical modeling of phycocyanin (PC), a unique inland waters cyanobacteria pigment. However, due to the small number of sensors with a spectral band of the PC absorption feature, it is difficult to develop semi-analytical models. This study evaluated the use of an empirical model to identify CHABs using TM and ETM+ sensors aboard Landsat 5 and 7 satellites. Five images were acquired for applying the model. Besides the images, data was also collected in the Guarapiranga Reservoir, in São Paulo Metropolitan Region, regarding the cyanobacteria cell count (cells/mL), which was used as an indicator of CHABs biomass. When model values were analyzed excluding calibration factors for temperate lakes, they showed a medium correlation (R²=0.81, p=0.036), while when the factors were included the model showed a high correlation (R²=0.96, p=0.003) to the cyanobacteria cell count. The empirical model analyzed proved useful as an important tool for policy makers, since it provided information regarding the horizontal distribution of CHABs which could not be acquired from traditional monitoring techniques.

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The goal of this paper is to present a methodology for quality control of horizontal geodetic networks through robustness and covariance analysis. In the proposed methodology, the positional accuracy of each point is estimated by a possible bias in their position (based on robustness analysis), in addition to its own positional precision (uncertainty) (through covariance analysis), being a measure independently from the choice of the datum. Besides presenting the theoretical development of the method, its application is demonstrated in a numerical example. The results indicate that, in general, the greater the distance of an unknown point to the control(s) point(s) of the network, the greater is the propagation of random errors on this unknown point, and the smaller the number of redundant observations around a unknown point, the greater the influence of possible (undetected) non-random errors on this point.

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The main topic of this paper is the Ambiguity Dilution of Precision known as ADOP. Basically, ADOP is defined as a diagnostic measure for assessing the precision of the float scalar ambiguities. Among the several possibilities, the ADOP can provide help in predicting the behavior of a baseline or a network of GNSS receivers, concerning the problem of ambiguity resolution, either in real-time (instantaneous) or in the post-processing mode. The main advantage of using ADOP is possibility of the extraction of a closed analytical expression, considering various factors that affect the ambiguity resolution. Furthermore, the ADOP is related to the success rate of ambiguity resolution. The expressions here used, takes into account several factors, for example, a priori information of the measurement precision of GNSS carrier phase and pseudorange, the number of stations and satellites, the number of available frequencies and the behavior of the atmosphere (ionosphere and troposphere). Several scenarios were established so as to analyze the impact of each factor in ambiguities resolution, within the context of some stations of the São Paulo GNSS network (GNSS-SP).

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Currently, the need of reliable coordinates has been one of the main objectives of the scientific and practice community. Thus, the robustness analysis of a geodetic network, aims, at analyzing if the network is robust or not, based on the maximum undetectable errors. The network will be robust if the influence of these errors is small, otherwise it is weak, or not robust. This analysis is performed with the merger of two techniques, one which deals with the statistical analysis of reliability and the other one with the geometric strength analysis. The reliability analysis will provide the maximum error that cannot be detected by tests, after the adjustment. After finding these errors, the geometric strength analysis will determine the potential strain that the network will have, based on these errors. It is emphasized that the robustness analysis doesn't depend of the datum, reflecting only the geometry of the network and the accuracy of the observations (VANÌCEK et al., 2001). Therefore, this work aims at contributing to the scientific research on geodetic networks, checking the same, based on their geometry and observations.

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Pós-graduação em Física - FEG

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The aim of this paper is to present an analytical solution for the spin motion equations of spin-stabilized satellite considering only the influence of solar radiation torque. The theory uses a cylindrical satellite on a circular orbit and considers that the satellite is always illuminated. The average components of this torque were determined over an orbital period. These components are substituted in the spin motion equations in order to get an analytical solution for the right ascension and declination of the satellite spin axis. The time evolution for the pointing deviation of the spin axis was also analyzed. These solutions were numerically implemented and compared with real data of the Brazilian Satellite of Data Collection - SCD1 an SCD2. The results show that the theory has consistency and can be applied to predict the spin motion of spin-stabilized artificial satellites.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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In this paper were studied regions close to the Roche lobe of a planet like Jupiter, in order to find regions with low velocities. We simulated a two dimensional and non-self-gravitating disk, where tidal and viscous torques are considered, using the hydrodynamic numerical integrator FARGO 2D. As stated earlier we are interested in find low velocities regions for in future works study the possibility of satellites formation in these regions.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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We present the results of a search for gravitational waves associated with 223 gamma-ray bursts (GRBs) detected by the InterPlanetary Network (IPN) in 2005-2010 during LIGO's fifth and sixth science runs and Virgo's first, second, and third science runs. The IPN satellites provide accurate times of the bursts and sky localizations that vary significantly from degree scale to hundreds of square degrees. We search for both a well-modeled binary coalescence signal, the favored progenitor model for short GRBs, and for generic, unmodeled gravitational wave bursts. Both searches use the event time and sky localization to improve the gravitational wave search sensitivity as compared to corresponding all-time, all-sky searches. We find no evidence of a gravitational wave signal associated with any of the IPN GRBs in the sample, nor do we find evidence for a population of weak gravitational wave signals associated with the GRBs. For all IPN-detected GRBs, for which a sufficient duration of quality gravitational wave data are available, we place lower bounds on the distance to the source in accordance with an optimistic assumption of gravitational wave emission energy of 10(-2)M(circle dot)c(2) at 150 Hz, and find a median of 13 Mpc. For the 27 short-hard GRBs we place 90% confidence exclusion distances to two source models: a binary neutron star coalescence, with a median distance of 12 Mpc, or the coalescence of a neutron star and black hole, with a median distance of 22 Mpc. Finally, we combine this search with previously published results to provide a population statement for GRB searches in first-generation LIGO and Virgo gravitational wave detectors and a resulting examination of prospects for the advanced gravitational wave detectors.