DATA INTEGRATION OF DIFFERENT DOMAINS IN GEO-INFORMATION MANAGEMENT: A RAILWAY INFRASTRUCTURE CASE STUDY

A 3D city model is a representation of an urban environment with a three-dimensional geometry of common urban objects and structures, with buildings as the most prominent feature. In the last decades, 3D city models appear to have been predominantly used for visualisation; however, nowadays they are being increasingly employed in a number of domains and for a broad range of tasks beyond visualisation. The MUIF (Modello Unico dell’Infrastruttura Fisica) project, here illustrated as a case study, refers to the implementation of a single spatial model of the infrastructure of Italy’s railway system (RFI). The authors describe preliminary results and the critical aspects of the study they are carrying out, explaining the processes and methodology to model all datasets into a single integrated spatial model as the reference base for future continuously updates. The case study refers to data collected by different sources and at various resolutions. An integrated spatial Database has been used for modelling topographic 3D objects, traditionally implemented in a 3D city model, as well as other specific 3D objects, related to the railway infrastructure that, usually, aren’t modelled in a 3D city model, following the same methodology as the first ones.</p

A Shapiro delay detection in the binary system hosting the millisecond pulsar PSR J1910-5959A

PSR J1910-5959A is a binary pulsar with a helium white dwarf companion located about 6 arcmin from the center of the globular cluster NGC6752. Based on 12 years of observations at the Parkes radio telescope, the relativistic Shapiro delay has been detected in this system. We obtain a companion mass Mc = 0.180+/-0.018Msun (1sigma) implying that the pulsar mass lies in the range 1.1Msun <= Mp <= 1.5Msun. We compare our results with previous optical determinations of the companion mass, and examine prospects for using this new measurement for calibrating the mass-radius relation for helium white dwarfs and for investigating their evolution in a pulsar binary system. Finally we examine the set of binary systems hosting a millisecond pulsar and a low mass helium white dwarf for which the mass of both stars has been measured. We confirm that the correlation between the companion mass and the orbital period predicted by Tauris & Savonije reproduces the observed values but find that the predicted Mp - Pb correlation over-estimates the neutron star mass by about 0.5Msun in the orbital period range covered by the observations. Moreover, a few systems do not obey the observed Mp - Pb correlation. We discuss these results in the framework of the mechanisms that inhibit the accretion of matter by a neutron star during its evolution in a low-mass X-ray binary.Comment: 4 figures, 2 tables, accepted for publication in the Astrophysical Journa

Placing limits on the stochastic gravitational-wave background using European Pulsar Timing Array data

Direct detection of low-frequency gravitational waves ($10^{-9} - 10^{-8}$ Hz) is the main goal of pulsar timing array (PTA) projects. One of the main targets for the PTAs is to measure the stochastic background of gravitational waves (GWB) whose characteristic strain is expected to approximately follow a power-law of the form $h_c(f)=A (f/\hbox{yr}^{-1})^{\alpha}$, where $f$ is the gravitational-wave frequency. In this paper we use the current data from the European PTA to determine an upper limit on the GWB amplitude $A$ as a function of the unknown spectral slope $\alpha$ with a Bayesian algorithm, by modelling the GWB as a random Gaussian process. For the case $\alpha=-2/3$, which is expected if the GWB is produced by supermassive black-hole binaries, we obtain a 95% confidence upper limit on $A$ of $6\times 10^{-15}$, which is 1.8 times lower than the 95% confidence GWB limit obtained by the Parkes PTA in 2006. Our approach to the data analysis incorporates the multi-telescope nature of the European PTA and thus can serve as a useful template for future intercontinental PTA collaborations.Comment: 14 pages, 8 figures, 3 tables, mnras accepte

EDUCATIONAL AND TRAINING EXPERIENCES IN GEOMATICS: TAILORED APPROACHES FOR DIFFERENT AUDIENCE

The recent outbreak of geospatial information to a wider audience, represents an inexorable flow made possible by the technological and scientific advances that cannot be opposed. The democratization of Geomatics technologies requires training opportunities with different level of complexity specifically tailored on the target audience and on the final purpose of the digitization process. In this frame, education plays a role of paramount importance, to create in the final users the awareness of the potentials of Geomatics-based technologies and of the quality control over the entire process.This paper outlines the current educational offer concerning the Geomatics Academic discipline in the Italian higher education system, highlighting the lack of dedicated path entirely devoted to the creation of specifically trained figure in this field. The comparison with the International panorama further stresses out this necessity. The purpose of this work is to present different educational approaches by distinguishing between the starting knowledge level of the students/participants and the final aim of the training activities. Three main audiences have been identified: i) experts, who already know some basics of Geomatics to understand the theoretical concepts behind its technologies; ii) intermediate audience, who are interested in learning about Geomatics technologies and methodologies, without any previous or poor education concerning these topics; iii) non-experts, a mix of a wide group of people, with different educations and interests, or without any interest at all.For each group, the multi-year experience concerning educational and training activities for the geomatics-based knowledge transfer in all the multi-level approaches of the GECO Lab (University of Florence) is presented.</p

Sardinia Radio Telescope wide-band spectral-polarimetric observations of the galaxy cluster 3C 129

We present new observations of the galaxy cluster 3C 129 obtained with the Sardinia Radio Telescope in the frequency range 6000-7200 MHz, with the aim to image the large-angular-scale emission at high-frequency of the radio sources located in this cluster of galaxies. The data were acquired using the recently-commissioned ROACH2-based backend to produce full-Stokes image cubes of an area of 1 deg x 1 deg centered on the radio source 3C 129. We modeled and deconvolved the telescope beam pattern from the data. We also measured the instrumental polarization beam patterns to correct the polarization images for off-axis instrumental polarization. Total intensity images at an angular resolution of 2.9 arcmin were obtained for the tailed radio galaxy 3C 129 and for 13 more sources in the field, including 3C 129.1 at the galaxy cluster center. These data were used, in combination with literature data at lower frequencies, to derive the variation of the synchrotron spectrum of 3C 129 along the tail of the radio source. If the magnetic field is at the equipartition value, we showed that the lifetimes of radiating electrons result in a radiative age for 3C 129 of t_syn = 267 +/- 26 Myrs. Assuming a linear projected length of 488 kpc for the tail, we deduced that 3C 129 is moving supersonically with a Mach number of M=v_gal/c_s=1.47. Linearly polarized emission was clearly detected for both 3C 129 and 3C 129.1. The linear polarization measured for 3C 129 reaches levels as high as 70% in the faintest region of the source where the magnetic field is aligned with the direction of the tail.Comment: 19 pages, 17 figures, accepted for publication in MNRA