Efficient implementation with FIR filters of operators based on B-splines to represent and classify signals of one and two dimensions

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Image registration techniques with multiresolution analysis in satellite oceanography

En aquest article es fa una descripció dels procediments realitzats per enregistrar dues imatges geomètricament, de forma automàtica, si es pren la primera com a imatge de referència. Es comparen els resultats obtinguts mitjançant tres mètodes. El primer mètode és el d’enregistrament clàssic en domini espacial maximitzant la correlació creuada (MCC)[1]. El segon mètode es basa en aplicar l’enregistrament MCC conjuntament amb un anàlisi multiescala a partir de transformades wavelet [2]. El tercer mètode és una variant de l’anterior que es situa a mig camí dels dos. Per cada un dels mètodes s’obté una estimació dels coeficients de la transformació que relaciona les dues imatges. A continuació es transforma per cada cas la segona imatge i es georeferencia respecte la primera. I per acabar es proposen unes mesures quantitatives que permeten discutir i comparar els resultats obtinguts amb cada mètode.In this paper we present processing techniques for automated image-to-image geometrical registration. One reference image is used to register the working image. Three methods are used. The first method is the classical image registration method using the maximum cross-correlation (MCC) in the spatial domain [1]. The second method is based on MCC and multiscale analysis through wavelet multiresolution techniques [2]. The third one is a fusion of the two previous methods. For each technique the transformation coefficients relating both images are estimated. Finally, the second image is transformed and georeferenced to the first one. In the conclusion, a proposal of quantitative parameters leads to a final discussion on the results.En este artículo se describen los procedimientos realizados para registrar geométricamente dos imágenes de forma automática si se toma la primera como imagen de referencia. Se comparan los resultados obtenidos mediante tres métodos. El primero es el método clásico para registrar dos imágenes en el dominio espacial maximizando la correlación cruzada (MCC) [1]. En el segundo se trata de aplicar de forma conjunta técnicas de análisis multiescalar, basadas en las transformaciones wavelet y el método MCC [2]. El tercero es una variación del segundo situada a medio camino de los dos métodos anteriores. Para cada método se obtiene una estimación de los coeficientes de la transformación que relaciona las dos imágenes. A continuación, se transforma la segunda imagen que se georreferencia respecto a la primera para cada caso. Para finalizar se proponen unas medidas cuantitativas que nos permiten discutir y comparar los resultados obtenidos en cada uno de los método

Density Local Discriminant Bases for the analysis of otolith morphology in fish identification applications

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Decimator filter based on B-splines

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Satellite image georegistration from coast-line codification

Martech 2007 International Workshop on Marine Technology, 15-16 november 2007, Vilanova i la Geltrú, Spain.-- 2 pages, 3 figuresThis paper presents a contour-based approach for automatic image registration in satellite oceanography. Accurate image georegistration is an essential step to increase the eff ectiveness of all the image processing methods that aggregate information from diff erent sources, i.e. applying data fusion techniques. In our approach the images description is based on main contours extracted from coast-line. Each contour is codifi ed by a modifi ed chain-code, and the result is a discrete value sequence. The classical registration techniques were area-based, and the registration was done in a 2D domain (spatial and/or transformed); this approach is feature-based, and the registration is done in a 1D domain (discrete sequences). This new technique improves the registration results. It allows the registration of multimodal images, and the registration when there are occlusions and gaps in the images (i.e. due to clouds), or the registration on images with moderate perspective changes. Finally, it has to be pointed out that the proposed contour-matching technique assumes that a reference image, containing the coastlines of the input image geographical area, is availablePeer reviewe

Satellite image georegistration from coast-line codification

This paper presents a contour-based approach for automatic image registration in satellite oceanography. Accurate image georegistration is an essential step to increase the eff ectiveness of all the image processing methods that aggregate information from diff erent sources, i.e. applying data fusion techniques. In our approach the images description is based on main contours extracted from coast-line. Each contour is codifi ed by a modifi ed chain-code, and the result is a discrete value sequence. The classical registration techniques were area-based, and the registration was done in a 2D domain (spatial and/or transformed); this approach is feature-based, and the registration is done in a 1D domain (discrete sequences). This new technique improves the registration results. It allows the registration of multimodal images, and the registration when there are occlusions and gaps in the images (i.e. due to clouds), or the registration on images with moderate perspective changes. Finally, it has to be pointed out that the proposed contour-matching technique assumes that a reference image, containing the coastlines of the input image geographical area, is available

Decimator filter based on B-splines

The cascaded integrator-comb (CIC) filters are widely used as decimators in many applications, such as in delta sigma AD converters to decimate the sampled signal on its output. One problem with these filters is that by increasing its order to improve the signal attenuation in the stop band, worsens the passband response. In this paper we propose a so-called least-squares filters (LSF) based on B-splines to improve that response, compensating for CIC filter drop and flattening the magnitude response of the pass band. We also study the relationship between the CIC filters, otherwise called moving average, and the B-splines expanded by an integer factor. We show that the least-squares filters based on B-splines can be decomposed in CIC filters, with a higher order than the splines used, plus a compensator filter. Another important contribution of this work are the FIR approximations of anti-causal IIR filters needed to implement LSFs.Peer ReviewedPostprint (published version

Efficient cubic spline interpolation implemented with FIR filters

Classical Cubic spline interpolation needs to solve a set of equations of high dimension. In this work we show how to compute the interpolant using a FIR digital filter, with a reduced number of operations per interpolated point and high accuracy. Additionally, the computation can be made on real time as the signal samples are acquired. Following this approach, we show how to obtain easily the derivatives of the interpolant in a similar way, and also signal approximations to reduce the oscillations that appear when using high order splines. These techniques are very well suited to compute continuous representations of image contours on closed shapes and to find its curvature and singularities.Peer ReviewedPostprint (published version

Data acquisition system for volcanic seismic

This paper presents a design that is being created for the acquisition of volcanic seismic data. This system is composed by a microcontroller to management the peripherals, a module to acquire the information of seismic sensor and the module of communications that is composed of the RF and the GPS system. The prototype will be a very low power system and it will allow work during a complete year.Postprint (published version