J. Piera

Publications of J. Piera

• Planning the installation of the European Multidisciplinary Sea-floor Observatory (EMSO): First approach using geographic information systems (GIS)

  Authors: I.F. Aymerich, J. Piera, J.J. Danobeitia

  OCEANS, 2011 IEEE - Spain; 07/2011

  The design, installation and maintenance of any submarine cable are difficult tasks necessary done for long-term submarine observatories. Cable installation and maintenance is one of the mostThe design, installation and maintenance of any submarine cable are difficult tasks necessary done for long-term submarine observatories. Cable installation and maintenance is one of the most expensive parts of a submarine cable system. To reduce costs, computer-based approaches are used for planning the installation and the maintenance of these networks. This contribution wants to briefly describe some basis to take into account in the framework of the European Multidisciplinary Sea-floor Observatory (EMSO). Quality improvements can reduce costs in cable installations. Submarine cable installation quantity is dramatically increasing, and these new tools minimize human error and reduce the added time at sea due to errors, reducing costs at the same time.

• Potential support vector machines and Self-Organizing Maps for phytoplankton discrimination

  Authors: I.F. Aymerich, J. Piera, A. Soria-Frisch

  Neural Networks (IJCNN), The 2010 International Joint Conference on; 08/2010

  Fluorescence spectroscopy is a powerful technique usually used to evaluate phytoplankton marine environments. In this study, a kernel method (Potential Support Vector Machine, P-SVM) is presented,Fluorescence spectroscopy is a powerful technique usually used to evaluate phytoplankton marine environments. In this study, a kernel method (Potential Support Vector Machine, P-SVM) is presented, evaluating its capability to achieve phytoplankton classification from its fluorescence spectra. Different phytoplankton species were studied, and their fluorescence spectra were acquired in laboratory. In a previous study working with Self-Organizing Maps (SOM), it was proved with experimental data from laboratory that excitation spectra were more discriminative than emission spectra. It was also shown that using some preprocessing techniques, such as derivative analysis, the classification performance from emission fluorescence data can be improved. The classification results were encouraging to keep working with emission fluorescence, and herein we present a comparison between P-SVM and SOM for this goal.

• Fast phytoplankton classification from fluorescence spectra: comparison between PSVM and SOM

  Authors: I.F. Aymerich, J. Piera, J. Mohr, A. Soria-Frisch, K. Obermayer

  OCEANS 2009 - EUROPE; 06/2009

  Evaluation of phytoplankton communities is an important task to characterize marine environments. Fluorescence spectroscopy is a powerful technique usually used for this goal. This study presents aEvaluation of phytoplankton communities is an important task to characterize marine environments. Fluorescence spectroscopy is a powerful technique usually used for this goal. This study presents a comparison between two different techniques for fast phytoplankton discrimination: Self-Organizing Maps (SOM) and Potential Support Vector Machines (P-SVM), evaluating its capability to achieve phytoplankton classification from its fluorescence spectra. Several cultures representing different algae groups were grown under the same conditions and their emission fluorescence spectra were measured every day. Finally, the classification results obtained from both techniques, SOM and P-SVM, are presented. In the case of using emission fluorescence spectra, the results show that we are able to reduce the acquisition time required for some of the existing techniques, obtaining encouraging classification performance.

• A Low-Power Datalogger Based on CompactFlash Memory for Ocean Bottom Seismometers

  Authors: S.S. Panahi, S. Ventosa, J. Cadena, A. Manuel-Lazaro, A. Bermudez, V. Sallares, J. Piera

  Instrumentation and Measurement, IEEE Transactions on. 11/2008;

  In the last decade, marine scientific instruments have been in high demand, particularly autonomous instruments that are capable of staying under water for a long time while performing continuousIn the last decade, marine scientific instruments have been in high demand, particularly autonomous instruments that are capable of staying under water for a long time while performing continuous data acquisition and storage. This paper introduces an instrument under development that is used for the study of ocean bottom sublayers and microseismic detection. The power consumption of the equipment has been minimized to increase autonomy, and Compact Flash memory cards have been used as the storage element. Development of such equipment is a joint effort between different disciplines, such as electronics, mechanics, geophysics, underwater communications, etc. The acquisition system was tested both in the laboratory and under real environmental conditions in the summer of 2005, and the results have been evaluated.

• Stray-light correction of in-water array spectroradiometers. Effects on underwater optical measurements

  Authors: E. Torrecilla, S. Pons, M. Vilaseca, J. Piera, J. Pujol

  OCEANS 2008; 10/2008

  Two miniature hyperspectral sensors are being considered to become part of a marine observatory system. The effect of stray-light radiation on its response is discussed in this article. A new methodTwo miniature hyperspectral sensors are being considered to become part of a marine observatory system. The effect of stray-light radiation on its response is discussed in this article. A new method to correct the unwanted spectral stray-light radiation has been developed and applied to both hyperspectral sensors. The correction method has been proved as effective for both considered miniature spectrographs using different calibration light sources. Furthermore, preliminary results of spectral stray-light corrections applied to underwater light field measurements point out that spectral stray-light correction plays an important role in accurate underwater optical hyperspectral measurements and its later spectral analysis.

• Effect of spectral resolution in hyperspectral data analysis

  Authors: E. Torrecilla, I.F. Aymerich, S. Pons, J. Piera

  Geoscience and Remote Sensing Symposium, 2007. IGARSS 2007. IEEE International; 08/2007

  The effect of hyperspectral data resolution on the results obtained using derivative spectroscopy is discussed in this article. A comparison was made between attenuation spectra measured using twoThe effect of hyperspectral data resolution on the results obtained using derivative spectroscopy is discussed in this article. A comparison was made between attenuation spectra measured using two different hyperspectral sensors with 3648 and 256 spectral bands, respectively. Smoothing and derivative algorithms were applied to both types of spectral data in order to assess qualitative information from the spectral features of several laboratory samples. In order to make an optimal application of the derivative analysis, a suitable selection of the smoothing and derivating parameters was done according to the resolution of each type of hyperspectral data. Second derivative spectra were obtained and peaks related to the absorption bands of pigments present in the considered samples were identified in both cases. Furthermore, interpolation techniques were applied so as to match spectral resolutions of data collected by the two sensors and negligible variations in the positions of the peaks were achieved in the derivative spectra.

• Monolithic spectrometer for environmental monitoring applications

  Authors: S. Pons, I.F. Aymerich, E. Torrecilla, J. Piera

  OCEANS 2007 - Europe; 07/2007

  Hyperspectral data analysis has been shown to be a reliable technique to identify several water components. Currently, there are numerous commercially available miniature spectrometer systems as wellHyperspectral data analysis has been shown to be a reliable technique to identify several water components. Currently, there are numerous commercially available miniature spectrometer systems as well as discrete components that are used by researchers in designing their own systems. We have developed a custom-designed hyperspectral sensor. Experimental results and potential applications are discussed on this article. It can be used as a low cost optical monitoring system to be employed on fish farming and aquaculture facilities.

• Wavelet Denoising Technique: Non white Gaussian noise reduction on oceanic microstructure data

  Authors: R. Quesada, J. Piera

  OCEANS 2007 - Europe; 07/2007

  Analysis of microstructure vertical profiles CTD (conductivity, temperature and depth) is a common method for characterizing environmental turbulent fluid dynamics. One of the objectives in analyzingAnalysis of microstructure vertical profiles CTD (conductivity, temperature and depth) is a common method for characterizing environmental turbulent fluid dynamics. One of the objectives in analyzing high-resolution CTD profiles is to identify turbulent regions (patches) within the flow. Due to the instrumental noise of CTD measurements and the environmental characteristics, it is necessary a denoising process before the data analysis. The approaches presented in the literature for turbulent patch identification are usually unable to identify patches at low-density gradient. A new method was proposed in [1] to improve patch detection at low-density gradients. The method, pointed out the influence of wavelet mother selection and the noise characterization on the final denoising results. This article introduces a procedure to obtain the optimal wavelet filters selection to reduce noise effects. In the literature the studies based in wavelet denoising are focused on reduce the effects of white Gaussian noise. In turn, in this study, the signal representing the noise is synthetically created and modelled by both flicker and white Gaussian noise. Numerical results indicate that the selected wavelet optimize the denoising method presented in [1] and show the importance of optimizing the denoising process to identify patches in a wide range of density gradients.

• Monolithic spectrometer for environmental monitoring applications

  Authors: S. Pons, IF Aymerich, E. Torrecilla, J. Piera

  OCEANS 2007-Europe. 01/2007;

• Effect of spectral resolution in hyperspectral data analysis

  Authors: E. Torrecilla, I.F. Aymerich, S. Pons, J. Piera

  01/2007

  The effect of hyperspectral data resolution on the results obtained using derivative spectroscopy is discussed in this article. A comparison was made between attenuation spectra measured using twoThe effect of hyperspectral data resolution on the results obtained using derivative spectroscopy is discussed in this article. A comparison was made between attenuation spectra measured using two different hyperspectral sensors with 3648 and 256 spectral bands, respectively. Smoothing and derivative algorithms were applied to both types of spectral data in order to assess qualitative information from the spectral features of several laboratory samples. In order to make an optimal application of the derivative analysis, a suitable selection of the smoothing and derivating parameters was done according to the resolution of each type of hyperspectral data. Second derivative spectra were obtained and peaks related to the absorption bands of pigments present in the considered samples were identified in both cases. Furthermore, interpolation techniques were applied so as to match spectral resolutions of data collected by the two sensors and negligible variations in the positions of the peaks were achieved i

• Comparative response of two different hyperspectral sensors. Application to derivative analysis of absorption spectra

  Authors: E. Torrecilla, S. Pons, I.F. Aymerich, J. Piera

  Instrumentation ViewPoint. 01/2007; 6:86--87.

• Low cost hyperspectral device suitable for monitoring sensor networks

  Authors: S. Pons, I.F. Aymerich, E. Torrecilla, J. Piera

  Instrumentation ViewPoint. 01/2007; 6:60--61.

• Software Tools for a Distributed Temperature Measurement Systems

  Authors: A. Manuel, J.D. Rio, S. Shariat, J. Piera, R. Palomera

  Instrumentation and Measurement Technology Conference, 2005. IMTC 2005. Proceedings of the IEEE; 06/2005

  This paper proposes to develop new software tools that has been applied in a low cost distributed temperature measurement system As measurement system base, an open field bus made of 2 cables whoseThis paper proposes to develop new software tools that has been applied in a low cost distributed temperature measurement system As measurement system base, an open field bus made of 2 cables whose addressing capacity is best, supporting cable lengths higher than 300m without the need of repeaters or signal re-generators with possibility of being integrated in an Ethernet environment, has been built.

• Characterizing the Response of Aquatic Systems to Wind Burst Forcing by Using High-Resolution Spatial Sensors.

  Authors: J. Piera, R. Quesada, S. Shariat Panahi, A. Manuel-Lazaro

  Instrumentation and Measurement Technology Conference, 2005. IMTC 2005. Proceedings of the IEEE; 06/2005

  The characterization of the turbulent environmental flow is an important research topic to improve the overall knowledge of ocean dynamics. In this paper we analyze different methodologies toThe characterization of the turbulent environmental flow is an important research topic to improve the overall knowledge of ocean dynamics. In this paper we analyze different methodologies to characterize the event processes (turbulent patches) associated to the environmental turbulent flow. The analysis of the transient response from a wind burst has been used as a framework for determining the best method of turbulent characterization based on different measurement systems

• A Low Power Datalogger based on Compactflash memory for Ocean Bottom Seismometers (OBS)

  Authors: S.S. Panahi, S. Ventosa, J. Cadena, A. Manuel, T. Bermudez, V. Sallares, J. Piera, J. Del Rio

  Instrumentation and Measurement Technology Conference, 2005. IMTC 2005. Proceedings of the IEEE; 06/2005

  In the last decade marine scientific exploration instruments are highly under demand, especially autonomous instruments capable of staying under water long period of time while performing continuousIn the last decade marine scientific exploration instruments are highly under demand, especially autonomous instruments capable of staying under water long period of time while performing continuous data acquisition and storage. This paper introduces an instrument presently under development used for the study of ocean bottom sub-layers as well as microseismic detection where power consumption has been minimized to increase autonomy and Compactflash memory cards have been used as the storage element. Development of such equipment is a joint work between different disciplines as electronics, mechanics, geophysics, underwater communications, etc. Currently acquisition system is under test in the laboratory and is going to be tested in real environmental conditions in summer 2005 where the results will be evaluated

• Turbulent oceanic flow characterization derived from high-resolution CTD data processing

  Authors: R. Quesada, J. Piera, I. Fernández, E. Torrecilla, S. Pons

  Instrumentation ViewPoint. 01/2005; 4:31--32.

• An instrumentation project for studying the effects of turbulence in aquatic systems

  Authors: J. Piera, R. Quesada, E. Torrecilla, I. Fernández, S. Pons

  Instrumentation ViewPoint. 01/2005; 4:30--31.

• Characterization of the water optical properties using hyperspectral sensors

  Authors: E. Torrecilla, J. Piera, R. Quesada, I. Fernández, S. Pons

  Instrumentation ViewPoint. 01/2005; 4:48--49.

• Wavelet denoising technique for high-resolution CTD data. Characterization of turbulent oceanic flow

  Authors: J. Piera, R. Quesada, A. Manuel-Lazaro, R.J. Del, S. Shariat Panahi, G. Olivar

  Sensors, 2004. Proceedings of IEEE; 11/2004

  The analysis of high-resolution CTD vertical profiles (conductivity, temperature and depth) is a common method for characterizing environmental turbulent fluid dynamics. One of the objectives inThe analysis of high-resolution CTD vertical profiles (conductivity, temperature and depth) is a common method for characterizing environmental turbulent fluid dynamics. One of the objectives in analyzing high-resolution CTD profiles is to identify turbulent regions (patches) within the flow. Due to the instrumental noise of CTD measurements, the previous methods for turbulent patch identification, reported in the literature, are usually unable to identify patches at low-density gradient. Here we proposed a new method that significantly improves patch detection at low-density gradients. The method is based on a wavelet-denoising procedure and a theoretical analysis of the error in data obtained from the CTD sensors. The high percentage of validating patches, obtained in numerical and field tests, indicates that the method is a powerful tool for fluid dynamics characterization, and can be applied in a wide range of environmental monitoring applications.

• Control of Monolithic Spectrometer: Applications for environmental monitoring

  Authors: J. Piera, S. Pons, M. Merchan, R. Quesada

  Instrumentation ViewPoint. 01/2004; 4:8--9.