Surveying at the limits of local RTK networks: Test results from the perspective of high accuracy users     

Mª Selmira Garrido  Elena GiménezMª Clara de Lacy  Antonio J. Gil 《International Journal of Applied Earth Observation and Geoinformation》2011

Precise GNSS-based differential positioning in real time is usually known as the real-time kinematics (RTK) technique. RTK reduces the effects of orbit errors and ionospheric and tropospheric refraction by forming differences between the observables (e.g. double-differences). These effects, however, grow with increasing baseline length, although the use of corrections generated in real-time from an active GNSS network allows these distance-dependent errors to be reduced. This technology increases the reliability of the system and thereby the accuracy of real-time positioning. In this study, the test results of RTK positioning at different test points located in the border area between the Autonomous Communities of the Region of Murcia and the Community of Valencia, in SE Spain, are presented. The analysis is based on three GNSS local active networks present in this border area, namely MERISTEMUM, REGAM and ERVA networks. Test measurements with RTK rover were performed in this region in order to analyze the real-time services offered by these three networks. Moreover, precise coordinates for each test point were determined using Bernese 5.0. The results confirm that it is possible to achieve centimetre-scale accuracy with RTK positioning based on the networks studied, even in border regions.  相似文献   

On far field occurrence of seismically induced landslides   总被引：1，自引：0，他引：1  

J. Delgado  J. Garrido  C. López-Casado  S. Martino  J.A. Peláez 《Engineering Geology》2011,123(3):204

Earthquakes may induce landslides at large distances from the epicentral area. In the last two decades, there have been many studies of this phenomenon to determine the causes that contribute to the occurrence of landslides at very long distances from earthquake epicenter. In this study, which is based on previously published works, a worldwide database comprising 270 earthquakes, including 150 during the instrumental period, was compiled to analyse the features of those landslides that occur at much further distances than maximum expected distances. From the analysis of the compiled data, it was observed that susceptible slopes can be grouped into five broad geological categories: jointed rock, marly–clayey (cohesive) soils, granular alluvial and/or colluvial sediments, volcanic soils, and residual soil slopes. These categories were equally likely to be associated with far field disrupted landslides, whereas far field coherent landslides were more frequent on cohesive soil slopes. Other factors, along with slope susceptibility may also contribute to far field landslides and increase the size of the area affected. Among these factors, site effects, antecedent rain and occurrence of seismic series have been cited. The analysis of available data also showed that for events of the same magnitude, far field disrupted landslides may occur at greater distances than coherent ones. The same database has also been employed to determine, for the first time, the upper bound curves for the maximum observed epicentral distances of several types of landslides and the maximum area observed to be affected by landslides, both based on the epicentral intensity of the events.  相似文献   

Asteroseismology of the β Cephei star 12 (DD) Lacertae: photometric observations, pulsational frequency analysis and mode identification     

G. Handler  M. Jerzykiewicz  E. Rodríguez  K. Uytterhoeven  P. J. Amado  T. N. Dorokhova  N. I. Dorokhov  E. Poretti  J.-P. Sareyan  L. Parrao  D. Lorenz  D. Zsuffa  R. Drummond  J. Daszy&#;ska-Daszkiewicz  T. Verhoelst  J. De Ridder  B. Acke  P.-O. Bourge  A. I. Movchan  R. Garrido  M. Paparó  T. Sahin  V. Antoci  S. N. Udovichenko  K. Csorba  R. Crowe  B. Berkey  S. Stewart  D. Terry  D. E. Mkrtichian  C. Aerts 《Monthly notices of the Royal Astronomical Society》2006,365(1):327-338

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Photometric Studies of O-type Hot Subdwarfs     

C. Rodríguez López  A. Ulla  R. Garrido  M. Manteiga  P. Thejll 《Astrophysics and Space Science》2004,291(3-4):431-434

We present a photometric study of eight sdOs and one sdOB on which simultaneous photometry in four Strömgren filters was performed. Our study seeks to detect the possible pulsators among the candidates.  相似文献   

GHASP: A 3-D Survey of Spiral and Irregular Galaxies at Hα     

P. Amram  C. Adami  C. Balkowski  S. Blais-Ouellette  A. Boselli  J. Boulesteix  C. Carignan  V. Cayatte  L. Chemin  J.L. Gach  O. Garrido  O. Hernandez  M. Marcelin  L. Michel-Dansac  H. Plana  D. Russeil  B. Vollmer  H. Wozniak 《Astrophysics and Space Science》2002,281(1-2):393-396

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Impact of tropospheric modelling on GNSS vertical precision: an empirical analysis based on a local active network     

Mª Selmira Garrido  Mª Clara de Lacy  Ana Mª Rojas 《International Journal of Digital Earth》2018,11(9):880-896

The troposphere affects Global Navigation Satellite System (GNSS) signals due to the variability of the refractive index. Tropospheric delay is a function of the satellite elevation angle and the altitude of the GNSS receiver and depends on the atmospheric parameters. If the residual tropospheric delay is not modelled carefully a bias error will occur in the vertical component. In order to analyse the precise altimetric positioning based on a local active network, four scenarios in Southern Spain with different topographical, environmental, and meteorological conditions are presented, considering both favourable and non-favourable conditions. The use of surface meteorological observations allows us to take into account the tropospheric conditions instead of a standard atmosphere, but introduces a residual tropospheric bias which reduces the accuracy of precise GNSS positioning. Thus, with short observation times it is recommended not to estimate troposphere parameters, but to use an a priori model together with the standard atmosphere. The results confirm that it is possible to achieve centimetre-scale vertical accuracy and precision with real time kinematic positioning even with large elevation differences with respect to the nearest reference stations. These numerical results may be taken into consideration for improving the altimetric configuration of the local active network.  相似文献   

FIRST radio counterpart candidates to ULXs: a catalogue     

D. Pérez-Ramírez  J. R. Sánchez-Sutil  A. Muñoz-Arjonilla  J. Martí  J. L. Garrido  P. Luque-Escamilla 《Astrophysics and Space Science》2007,309(1-4):147-150

Ultraluminous X-ray sources (ULXs) are the most luminous discrete X-ray sources (excluding AGNs) in the local Universe with observed luminosities above, and in many cases in excess of, 10³⁹ erg?s^?1. Their physical nature is still uncertain, and many models have been proposed to explain their unusual luminosities. Some of them favour the possible nature of these objects as extragalactic microquasars with strong beaming effects. Others, instead, rely on accretion onto intermediate-mass black holes. In any case, both interpretations offer perspectives for possible gamma-ray detections by future space missions. In order to help to constrain at present the ULX physical nature, we provide here an account of our search for radio counterparts to ULXs located in nearby galaxies, based on a systematic cross-identification of the most recent, available and extensive ULX catalogues and radio archival data. Although we ended up with 70 positional coincidences, most of them were located within the nuclear regions of these galaxies, and thus, they do not represent true ULXs. However, among these sources we identify 11 remarkable cases not previously reported of ULX and radio emission coincidence. Future follow up of these promising cases with a multi-wavelength approach could be useful to improve our understanding of the ULX phenomenon.  相似文献   

Spatial distribution and vertical migrations of fish larvae communities off Northwestern Iberia sampled with LHPR and Bongo nets     

Susana Garrido  A. Miguel P. Santos  Antonina dos Santos  Pedro R 《Estuarine, Coastal and Shelf Science》2009,84(4):463-475

The spatial distribution and diel vertical migration of fish larvae were studied in relation to the environmental conditions off NW Iberia during May 2002. Larvae from 23 families were identified, the most abundant were the Clupeidae, Gobiidae, Callionymidae, Blenniidae, Sparidae and Labridae. Sardina pilchardus was the most abundant species, mean concentrations 1 order of magnitude higher than the other fish larvae species. Larval horizontal distribution was mainly related to upwelling-driven circulation, resulting in an offshore increase of larval abundance while the vertical distribution was closely associated to the Western Iberia Buoyant Plume. Despite this general trend, taxon-specific relationships between the distribution of larvae and environmental variables were observed, and temperature was an important regressor explaining the distribution of most taxa. A comparison between ichthyoplankton samples collected alternatively with the LHPR and Bongo nets resulted in captures of larvae ≈1 order of magnitude higher for the LHPR, probably related to its higher towing speed. The spatial distribution and relative composition of larvae were also different for both nets, although the most frequent/abundant groups were the same. A fixed station sampled for 69-h showed diel vertical migrations performed by the larvae, with the highest larval concentrations occurring at surface layers during the night and most larvae being found in the neuston layer only during that period.  相似文献   

Intraspecific diet shift in Talitrus saltator inhabiting exposed sandy beaches     

Celia Olabarria  Mónica Incera  Josefina Garrido  Iván F. Rodil  Francesca Rossi 《Estuarine, Coastal and Shelf Science》2009

Talitrid amphipods are the most abundant herbivores on exposed sandy beaches. Despite their important role as trophic intermediates between macrophytes and higher levels (i.e. insect and bird) of beach food webs, very little information is available on their feeding patterns. The main aim of this study was to investigate intraspecific differences in the feeding behaviour of Talitrus saltator. We tested the hypotheses that: (1) adult females and males showed different isotope signatures and therefore relied on different sources of food; and (2) patterns of variation of isotope signatures of juveniles differed from those of adult specimens, evidencing a diet shift during the development. We used stable isotope signatures and tested for differences upon the level on the shore, times of the year and beaches experiencing similar morpho-dynamic and environmental conditions. Finally, we investigated the trophic significance of macrophyte detritus in the diet of males, females and juveniles. Results showed that adult males had a more variable diet than females and juveniles (inferred from δ¹³C and δ¹⁵N values). Dual-isotope graphs suggested that Sargassum muticum and Cystoseira baccata wrack could be among the main food sources for both juvenile and adult stage.  相似文献   

Time-dependent convection seismic study of five γ Doradus stars     

M.-A. Dupret  A. Grigahcène  R. Garrido  J. De Ridder  R. Scuflaire  M. Gabriel 《Monthly notices of the Royal Astronomical Society》2005,360(3):1143-1152

We apply for the first time the time-dependent convection (TDC) treatment of Gabriel and Grigahcène et al. to the photometric mode identification in γ Doradus (γ Dor) stars. We consider the influence of this treatment on the theoretical amplitude ratios and phase differences. Comparison with the observed amplitudes and phases of the stars γ Dor, 9 Aurigae, HD 207223 = HR 8330, HD 12901 and 48501 is presented and enables us to identify the degree ℓ of the pulsation modes for four of them. We also determine the mode stability for different models of these stars. We show that our TDC models agree better with observations than with frozen convection models. Finally, we compare the results obtained with different values of the mixing-length parameter α.  相似文献