Synergetic efficiency of Lidar and WorldView-2 for 3D urban cartography in Northeast Mexico

Three-dimensional urban cartography is needed for city changes’ assessment. The variety of studies using 3D calculations of urban elements grows each year. Building and vegetation volumes are necessary to assess and understand spatio-temporal urban changeable environments. However, there are technical questions as to which method can improve 3D urban cartographic accuracy. The innovative part of this current study is the creation of a six-band hybrid obtained from LIDAR and WorldView2 synergy. Two different enhancement algorithms demonstrated the most important spectral features for the urban development and vegetation classes. Results indicated an improvement in accuracy by up to 21.3%, according to the Kappa coefficient. Both infra-red band and intensity band were the most significant, according to the principal components analysis. The synergy delimited classes and polygons, as well as the direct display of information regarding heights of elements and improving the extraction of roads, buildings and vegetation classes.     

A calibration system for superconducting gravimeters

A new method for the calibration of a superconducting gravity meter is described, in which a 273 Kg annular mass is placed around the meter and is moved up and down. The geometry of the apparatus is easy to model and the accuracy in the computation of the gravity variation induced by the mass, 6.7µgal, is limited only by the accuracy in the knowledge of value of the gravitational constant. Measurements done in 91 and 92 for the calibration of the instrument GWR-T015 are described. The calibration factor has been determined with a precision of about 0.3%.     

Changes of the profiles of spectral lines due to mass transfer in close binaries

In this paper, the model of the ring envelope round the primary component and the stream of the gaseous mass flowing from the secondary component to the primary is constructed on the basis of theoretical computations concerning the exchange of the mass between the components of the binary. The paper studies the influence of the gaseous mass on the profiles of spectral lines before and after occultation; the influence of the stream on the profile in case the secondary is near elongation, is also investigated. The line profiles obtained by numerical computations show that their changes caused by outflowing mass should be well detectable from spectrograms taken at particular phase of the binary. Changes in the lines may influence the measurement of radial velocities. The method for distinguishing the influence of the stream from the influence of the ring is described.     

Agricultural impacts on ecosystem functioning in temperate areas of North and South America

Land use has a large impact on ecosystem functioning, though evidences of these impacts at the regional scale are scarce. The objective of this paper was to analyze the impacts of agricultural land use on ecosystem functioning (radiation interception and carbon uptake) in temperate areas of North and South America. From land cover maps generated using high-resolution satellite images we selected sites dominated by row crops (RC), small grain crops (SG), pastures (PA), and rangelands (RA) in the Central Plains of USA and the Pampas of Argentina. These two regions share climatic characteristics and the agricultural conditions (crop types) are also very similar. Both areas were originally dominated by temperate grasslands. In these sites we extracted the temporal series of the normalized difference vegetation index (NDVI) from the NOAA satellites for the period 1989–1998 and calculated the mean seasonal NDVI curve for each site. Additionally, we calculated the mean annual NDVI, the maximum NDVI, the date of the year when the max NDVI was recorded and the interannual variability of these three attributes. We compared the mean values of each NDVI-derived attribute between land cover types and between continents. The NDVI seasonal patterns for each land cover type were roughly similar between the Central Plains and the Pampas during the growing season. The largest differences were observed during the winter and spring, when the NDVI of all land cover types in the Central Plains remained at lower values than in the Pampas. This was probably caused by the high annual thermal amplitude in the Central Plains that results in a much more restricted growing season. As a result of these differences in the shape of the NDVI curve, the mean annual NDVI in the Central Plains was lower than in the Pampas for all land cover types but the maximum NDVI did not differ importantly. In both regions, row crops delayed the date of the NDVI peak, small grain crops advanced it and pastures did not change it importantly, compared with rangelands. The interannual variability of the NDVI attributes was higher for small grains than for row crops in both regions. However, small grains crops were consistently more variable between years in the Central Plains than in the Pampas. The opposite occurred with pastures and rangelands, which were more variable in the Pampas than in the Central Plains. This paper confirms and generalizes previous findings that showed important imprints of land use on ecosystem functioning in temperate ecosystems. Our results support the idea that the changes in land cover that have occurred in the Central Plains and the Pampas leaded to similar changes in the way that ecosystems absorb solar radiation and in the patterns of carbon uptake.     

Airglow on Mars: Some model expectations for the OH Meinel bands and the O2 IR atmospheric band

This work presents model calculations of the diurnal airglow emissions from the OH Meinel bands and the O₂ IR atmospheric band in the neutral atmosphere of Mars. A time-dependent photochemical model of the lower atmosphere below 80 km has been developed for this purpose. Special emphasis is placed on the nightglow emissions because of their potential to characterize the atomic oxygen profile in the 50-80 km region. Unlike on Earth, the OH Meinel emission rates are very sensitive to the details of the vibrational relaxation pathway. In the sudden death and collisional cascade limits, the maximum OH Meinel column intensities for emissions originating from a fixed upper vibrational level are calculated to be about 300 R, for transitions v^′=9→v^′?8, and 15,000 R, for transitions v^′=1→v^′=0, respectively. During the daytime the 1.27 μm emission from O₂(), primarily formed from ozone photodissociation, is of the order of MegaRayleighs (MR). Due to the long radiative lifetime of O₂(), a luminescent remnant of the dayglow extends to the dark side for about two hours. At night, excited molecular oxygen is expected to be produced through the three body reaction O + O + CO₂. The column emission of this nighttime component of the airglow is estimated to amount to 25 kR. Both nightglow emissions, from the OH Meinel bands and the O₂ IR atmospheric band, overlap in the 50-80 km region. Photodissociation of CO₂ in the upper atmosphere and the subsequent transport of the atomic oxygen produced to the emitting layer are revealed as key factors in the nightglow emissions from these systems. The Mars 5 upper constraint for the product [H][O₃] is revised on the basis of more recent values for the emission probabilities and collisional deactivation coefficients.     

Spatial and temporal patterns of dry spell lengths in the Iberian Peninsula for the second half of the twentieth century

Summary Daily pluviometric records of 43 meteorological stations across the Iberian Peninsula have permitted a detailed analysis of dry spell patterns for the period 1951–2000 by distinguishing daily amount thresholds of 0.1, 1.0, 5.0 and 10.0 mm/day. The analyses are based on three annual series, namely the number of dry spells, N, the average dry spell length, L, and the extreme dry spell length, L _max. First, the statistical significance of local trends for the annual series of N, L and L _max has been investigated by means of the Mann-Kendall test and significant field trends have been established by means of Monte Carlo simulations. Clear signs of negative field trends are detected for N (1.0 and 10.0 mm/day) and L (0.1 mm/day). Second, the Weibull model fits well the empirical distributions of dry spell lengths for all the rain gauges, whatever the daily amount threshold, with a well ranged spatial distribution of their parameters u and k. On the basis of the Weibull distribution, return period maps for 2, 5, 10, 25 and 50 years have been obtained for dry spell lengths with respect to the four daily threshold levels. While for 0.1 and 1.0 mm/day the longest dry spells are expected at the south of the Iberian Peninsula, for 5.0 and 10.0 mm/day they are mostly detected at the southeast. Finally, the elapsed time between consecutive dry spells has been analysed by considering the same rain amount thresholds and different dry spell lengths at increasing intervals of 10 days. This analysis makes evident a significant negative field trend of the elapsed time between consecutive dry spells of lengths ranging from 10 to 20 days for daily amount thresholds of 1.0, 5.0 and 10.0 mm/day. Authors’ addresses: X. Lana, C. Serra, Departament de Física i Enginyeria Nuclear, ETSEIB, Universitat Politècnica de Catalunya, Av. Diagonal 647 planta 11, 08028 Barcelona, Spain; M. D. Marínez, Departament de Física Aplicada, Universitat Politècnica de Catalunya, 08028 Barcelona, Spain; A. Burgue?o, Departament de Meteorologia i Astronomia, Universitat de Barcelona, 08028 Barcelona, Spain; J. Martín-Vide, L. Gómez, Grup de Climatologia, Universitat de Barcelona, 08028 Barcelona, Spain.     

Numerical solution to the oblique derivative boundary value problem on non-uniform grids above the Earth topography

The paper presents a numerical solution of the oblique derivative boundary value problem on and above the Earth’s topography using the finite volume method (FVM). It introduces a novel method for constructing non-uniform hexahedron 3D grids above the Earth’s surface. It is based on an evolution of a surface, which approximates the Earth’s topography, by mean curvature. To obtain optimal shapes of non-uniform 3D grid, the proposed evolution is accompanied by a tangential redistribution of grid nodes. Afterwards, the Laplace equation is discretized using FVM developed for such a non-uniform grid. The oblique derivative boundary condition is treated as a stationary advection equation, and we derive a new upwind type discretization suitable for non-uniform 3D grids. The discretization of the Laplace equation together with the discretization of the oblique derivative boundary condition leads to a linear system of equations. The solution of this system gives the disturbing potential in the whole computational domain including the Earth’s surface. Numerical experiments aim to show properties and demonstrate efficiency of the developed FVM approach. The first experiments study an experimental order of convergence of the method. Then, a reconstruction of the harmonic function on the Earth’s topography, which is generated from the EGM2008 or EIGEN-6C4 global geopotential model, is presented. The obtained FVM solutions show that refining of the computational grid leads to more precise results. The last experiment deals with local gravity field modelling in Slovakia using terrestrial gravity data. The GNSS-levelling test shows accuracy of the obtained local quasigeoid model.     

An open source GIS‐based Planning Support System: Application to the land use plan of La Troncal,Ecuador

Planning Support Systems (PSS) comprise a wide variety of geo‐technological tools related to GIS and spatial modeling aimed at addressing land planning processes. This article describes the OpenRules system, a PSS based on a previous system called RULES. Among OpenRules new features are its architecture, based exclusively on free and open source software, and its applicability to all land use types, including rural and urban uses. In addition, OpenRules incorporates an unlimited number of land evaluation factors and a new objective in land use spatial allocation. OpenRules has been programmed in Java and implemented as a module of the free GIS software gvSIG, with full integration between the GIS and the decision support tools. Decision support tools include multicriteria evaluation, multiobjective linear programming and heuristic techniques, which support three basic stages of land use planning processes, namely land suitability evaluation, land use area optimization and land use spatial allocation. The application of OpenRules to the region of La Troncal, Ecuador, demonstrates its capability to generate alternative and coherent solutions through a scientific and justified procedure at low cost in terms of time and resources.     

Mortality by cause of death in Colombia: a local analysis using spatial econometrics

Journal of Geographical Systems - Colombia is undergoing major changes in mortality patterns. National- and department-level cause-specific analyses have previously been carried out, but very...