The economic impact of climate change on urban drainage master planning in Barcelona

In the context of global change, urban drainage infrastructures must be planned considering future challenges such as new climate change and urban growth scenarios. Large cities require master plans to properly rank and schedule infrastructure development. The flood mitigation measures proposed in previous plans must be revised and updated to address future urban challenges with special regard to climate scenarios. Regarding risk assessment, there is no linear relationship between an increase in rainfall and an increase in risk value. For risk management, the relationship between an increase in rainfall increase and the budget for mitigation measures is even more complex. To investigate this relationship and the economic impact of the aforementioned up-date, a new plan should be elaborated. Urban drainage master plans have been developed in Barcelona city for the last 50 years. In terms of rainfall, the impact of climate change has been established to be an increase of 7–26% at peak intensity, depending on rainfall duration. The Integral Drainage Master Plan of Barcelona (PDISBA) addresses these new challenges. The modification of rainfall scenario planning and the typology of mitigation measures result in an important rise in investment budget, infrastructure life cycle, and operation and maintenance budgets for said infrastructure. The total cost of the planned measures outlined in the PDISBA has risen to €1.442 million, nearly double that of the previous plan developed in 2006

Modeling of the GNSS Directional Radio Channel in Urban Areas Based on Synthetic Environments

This paper presents an approach to simulation of the GNSS directional channel based on the combination of physical and statistical methods of modeling. The key element of the model is the use of synthetic environment to represent general properties of types of environment: rural, urban, sub-urban etc. Spatial-domain characteristics of the multipath signals (time delay, angle of arrival and angular spread) are extracted with a simple geometric ray-tracing applied to the synthetic environment. Other parameters (power and fading characteristics) are obtained with a stochastic model for a land mobile satellite channel. Due to that combination of the methodsthe derived channel model preserves the speed and generality of stochastic models and allows to obtain the directional signal information by an intuitively understandble way

Estimation of Synchronization Parameters using SAGE in a GNSS-Receiver

The quality of the data presented to the user in a GNSS (Global Navigation Satellite System)-receiver depends largely on the accuracy in the propagation delay estimation of the direct signal (line-of-sight signal, LOSS). Under the presence of multipath signals, a standard navigation receiver that is designed to synchronize a single signal replica through conventional circuits (Delay-Lock Loop, DLL) experiences an error in the pseudorange measurement, the so-called multipath error. For the current GPS C/A signal, this error can range from a few metres up to more than 100 metres. The synchronization of a navigation signal is usually performed by a DLL, which basically implements an approximation of the maximum likelihood estimator (MLE). The problem which arises is that the order of this estimator (the DLL) is chosen according to the assumption that only the LOSS is present. This means that this estimator tries to estimate the relative propagation delay of only one signal replica. In case the LOSS is corrupted by several superimposed delayed replicas this estimator becomes biased, because of the change of the order of the incident estimation problem. Thus, in order to perform synchronization in the presence of multipath corrupted signals we follow the approach of obtaining the MLE for estimation problems of higher order. Therefore, signal parameters of a number of superimposed delayed replicas have to be estimated jointly. As this leads to a multi-dimensional non-linear optimization problem the reduction of the complexity of this problem is the most important issue to be solved in order to perform precise positioning in a navigation receiver. Several techniques have been proposed in the literature to solve the multipath problem in navigation receivers, like the well known MEDLL [1]. Recently, interesting approaches like in [2] and in [3] have appeared. The first applies the maximum likelihood principle to the delay estimation in the presence of multipath and unintentional interference in an antenna array receiver, and the latter develops efficient multipath mitigation techniques (with low-complexity) in single antenna and array antenna navigation receivers. In both works, a connection is made between the multipath estimation problem in navigation systems and the same problem in communication systems. In this work the potential of the SAGE (Space-Alternating Generalized Expectation Maximization) algorithm for global navigation satellite systems in order to estimate synchronization parameters of the LOSS under the presence of multipath signals is to be considered. The SAGE algorithm is a low-complexity generalization of the EM (Expectation Maximization) algorithm, which iteratively approximates the MLE. It breaks down the multi-dimensional non-linear optimization problem which arises for the general maximum likelihood problem that usually is to complex to be solved with reasonable effort into problems of lower dimensions. Due to this significant reduction of complexity and its fast convergence the SAGE algorithm has been successfully applied for parameter estimation (relative delay, incident azimuth, incident elevation, Doppler frequency, and complex amplitude) in direct-sequence code-division multiple access systems (DS-CDMA) in mobile radio environments. This study discusses receivers with a single antenna, and also points out the capabilities of the proposed techniques using multiple antennas (array processing), for the application in a GNSS environment. Whereas for the single antenna case we estimate the complex amplitudes and the relative delays of the impinging waves, in the latter additionally the spatial signature (incident azimuth and incident elevation) is estimated. The performance of the algorithm is assessed by computer simulations using a simple spatial channel model and a model for the aeronautical multipath navigation channel (European Space Agency, ESA: "Navigation signal measurement campaign for critical environments"). In order to describe the behaviour of the SAGE algorithm classical concepts like the RMSE (root mean square error) and the CRLB (Cramer-Rao lower bound) are employed. On the other hand simulations with the end-to-end simulator for satellite navigation systems NAVSIM developed by the German Aerospace Center (DLR) are made in order to assess the performance of the SAGE algorithm compared to the tracking performance of a conventional navigation receiver with a single antenna (non-coherent DLL, narrow correlator, Costas-Loop used as PLL). Furthermore, we discuss critical aspects which have to be considered using SAGE, like the initialisation problem or its complexity, and we propose an approach to an easy implementation. The results of the performed computer simulations and discussion indicate that the SAGE algorithm has the potential to be a very powerful high-resolution method to successfully estimate parameters of impinging waves for navigation systems. The presented approach to synchronization in GNSS-receivers has proven to be a promising method to efficiently combat multipath for navigation applications due to its good performance, fast convergence, and low complexity. [1] R. D. J. Van Nee, J. Siereveld, P. Fenton, and B. R. Townsend, " The Multipath Estimating Delay Lock Loop: Approaching Theoretical Accuracy Limits", Proc. IEEE Position, Location Navigation Symp., pp. 246-251, Apr. 1994. [2] Gonzalo Seco, "Antenna Arrays for Multipath and Interference Mitigation in GNSS Receivers", Ph.D. thesis, Department of Signal Theory and Communications, Universitat Politecnica Catalunya, 2000. [3] Jesus Selva Vera, "Efficient Mitigation in Navigation Systems", Ph.D. thesis, Department of Signal Theory and Communications, Universitat Politecnica Catalunya, 2004

Parameter Estimation Using SAGE in a GNSS-Receiver

The potential of the SAGE (Space-Alternating Generalised Expectation Maximisation) algorithm for navigation systems in order to distinguish the line-of-sight signal (LOSS) is to be considered. The SAGE algorithm is a low-complexity generalisation of the EM (Expectation-Maximisation) algorithm, which iteratively approximates the maximum likelihood estimator (MLE) and has been successfully applied for parameter estimation (relative delay, incident azimuth, incident elevation, Doppler frequency, and complex amplitude of impinging waves) in mobile radio environments. This study discusses receivers using a single antenna, and also points out the capabilities of this technique using multiple antennas (array processing), for the application in a GNSS (Global Navigation Satellite Systems) environment. Whereas for the single antenna case we estimate the complex amplitudes and relative delays of the impinging waves, in the latter additionally the spatial signature of the impinging waves (incident azimuth) is estimated. The results of the performed computer simulations and discussion indicate that the SAGE algorithm has the potential to be a very powerful high-resolution method to successfully estimate parameters of impinging waves for navigation systems. SAGE has proven to be a promising method to efficiently combat multipath for navigation applications due to its good performance, fast convergence, and low complexity

Connecting ISO and OGC Models to the Semantic Web

OGC and ISO have developed extensive standards for geospatial applications, providing well-founded definitions of concepts related to the geospatial domain. Currently these standards are available in textual descriptions supported by UML static structure diagrams, giving guidance to developers to implement applications. However, in an open and distributed environment, the possibility to assess the interoperability of applications and data sources without human intervention is becoming increasingly important. The current forms of representations hinder this attempt since UML is designed for model building and sharing by human experts. We propose to enforce the efforts to include such standards in the framework of the semantic web. This would leverage investment into these standardization efforts by opening sophisticated domain models to a wide range of potential users. The paper shows a first attempt at capturing the contents of some key ISO and OGC standards in a standard web ontology environment. We propose OWL as a candidate representation language since it is designed to provide guidance for intelligent processing methods (Falkovych, Sabou et al. 2003). Ontologies for the Geo-Domain In the context of the ACE-GIS projec

A compilation of field surveys on gaseous elemental mercury (GEM) from contrasting environmental settings in Europe, South America, South Africa and China: separating fads from facts

Mercury is transported globally in the atmosphere mostly in gaseous elemental form (GEM, Hggas 0), but still few worldwide studies taking into account different and contrasted environmental settings are available in a single publication. This work presents and discusses data from Argentina, Bolivia, Bosnia and Herzegovina, Brazil, Chile, China, Croatia, Finland, Italy, Russia, South Africa, Spain, Slovenia and Venezuela. We classified the information in four groups: (1) mining districts where this contaminant poses or has posed a risk for human populations and/or ecosystems; (2) cities, where the concentration of atmospheric mercury could be higher than normal due to the burning of fossil fuels and industrial activities; (3) areas with natural emissions from volcanoes; and (4) pristine areas where no anthropogenic influence was apparent. All the surveys were performed using portable LUMEX RA-915 series atomic absorption spectrometers. The results for cities fall within a low GEM concentration range that rarely exceeds 30 ng m-3, that is, 6.6 times lower than the restrictive ATSDR threshold (200 ng m-3) for chronic exposure to this pollutant. We also observed this behavior in the former mercury mining districts, where few data were above 200 ng m-3. We noted that high concentrations of GEM are localized phenomena that fade away in short distances. However, this does not imply that they do not pose a risk for those working in close proximity to the source. This is the case of the artisanal gold miners that heat the Au-Hg amalgam to vaporize mercury. In this respect, while GEM can be truly regarded as a hazard, because of possible physical-chemical transformations into other species, it is only under these localized conditions, implying exposure to high GEM concentrations, which it becomes a direct risk for humans.Peer ReviewedPostprint (published version