UBathy: a new approach for bathymetric inversion from video imagery

A new approach to infer the bathymetry from coastal video monitoring systems is presented. The methodology uses principal component analysis of the Hilbert transform of video images to obtain the components of the wave propagation field and their corresponding frequency and wavenumber. Incident and reflected constituents and subharmonics components are also found. Local water depth is then successfully estimated through wave dispersion relationship. The method is first applied to monochromatic and polychromatic synthetic wave trains propagated using linear wave theory over an alongshore uniform bathymetry in order to analyze the influence of different parameters on the results. To assess the ability of the approach to infer the bathymetry under more realistic conditions and to explore the influence of other parameters, nonlinear wave propagation is also performed using a fully nonlinear Boussinesq-type model over a complex bathymetry. In the synthetic cases, the relative root mean square error obtained in bathymetry recovery (for water depths 0.75m¿h¿8.0m) ranges from ~1% to ~3% for infinitesimal-amplitude wave cases (monochromatic or polychromatic) to ~15% in the most complex case (nonlinear polychromatic waves). Finally, the new methodology is satisfactorily validated through a real field site video.Postprint (published version

Aerodynamic analysis of the lift reducer device by flow transfer

From the beginnings of aviation and aeronautical world in general, it has searched the goal of creating a machine capable of taking off in a controlled way trying to achieve the highest operational aircraft. Always looking for the highest levels of speed, weight reduction, maneuverability, etc. In the initial stages of the history of aviation, to achieve these objectives, the mankind was witness of the creation of a large number of machines that approached these concepts from completely different paths. Finally, with the passage of the years, reached a basic design and configuration of it had to be a plane. In the following step and until these days, the aviation industry has focused on improving the existing design making it lighter, more maneuverable, with lower fuel consumption, safer and a long list of other improvements. However, always have been projects that have attempted to move away from this basic configuration making improvements, but in most cases they have not reached the success. In the next pages, you will find the analysis and possible implementations of one of these projects

Estimation of Azimuth Phase Undulations with Multisquint Processing in Airborne Interferometric SAR Images

This letter presents a technique to detect and correct phase errors appearing in interferometric airborne synthetic aperture radar (SAR) systems due to the lack of precision in the navigation system. The technique is based on a multisquint processing approach, i.e., by processing the same image pairs with different squint angles we can combine the information of different interferograms to obtain the desired phase correction. Airborne single-pass interferometric data from the Deutsches Zentrum für Luft- und Raumfahrt (DLR) Experimental airborne SAR is used to validate the metho

Procès de fabricació d'una boixa Formula Student

El present projecte pretén donar a conèixer els processos de mecanitzat, en el qual la matèria primera és l‟alumini. Es dissenyaran dues peces (mètode tradicional i per CNC) d‟un vehicle que forma part d‟una competició universitària anomenada Formula Student. La peça en qüestió és la boixa, encarregada de fer de suport de la mangueta i la platina del disc de fre, a més de servir d‟eix de rotació de la roda. El disseny ve condicionat pels requeriments de l‟equip pel qual s‟està treballant, el Vilanova Formula Team, amb el qual es tindrà una comunicació constant per a complir els seus requisits. Dins d‟aquest procés tradicional es controlen els paràmetres de la boixa, per tal d‟ajustar els costos a les seves necessitats. També es planifica la feina de l‟operari que durà a terme aquest procés, de manera que els temps de cada fase i les accions en cada fase quedaran definides per tal de fabricar aquesta peça de la manera més òptima possible. Tot i no haver pogut fabricar la peça en alumini per problemes de disponibilitat a la universitat, sí que s‟ha pogut dur a terme una simulació de la boixa en CNC mitjançant el programa de CAD NX. Inclús sabent que aquesta peça no serà la que finalment es muntarà al vehicle, doncs s‟haurien de fer nombroses proves i modificacions, és el primer pas, el més important doncs crea un punt de partida per a continuar treballant en el desenvolupament del monoplaça

A Versatile Processing Chain for Experimental TanDEM-X Product Evaluation

TanDEM-X is a high-resolution interferometric mission with the main goal of providing a global digital elevation model (DEM) of the Earth surface by means of single-pass X-band SAR interferometry. It is, moreover, the first genuinely bistatic spaceborne SAR mission, and, independently of its usual quasi-monostatic configuration, includes many of the peculiarities of bistatic SAR. An experimental, versatile, and flexible interferometric chain has been developed at DLR Microwaves and Radar Institute for the scientific exploitation of TanDEM-X data acquired in non-standard configurations. The paper describes the structure of the processing chain and focusses on some essential aspects of its bistatic part

Sentinel-1 Imaging Performance Verification with TerraSAR-X

This paper presents dedicated analyses of TerraSAR-X data with respect to the Sentinel-1 TOPS imaging mode. First, the analysis of Doppler centroid behaviour for high azimuth steering angles, as occurs in TOPS imaging, is investigated followed by the analysis and compensation of residual scalloping. Finally, the Flexible-Dynamic BAQ (FD-BAQ) raw data compression algorithm is investigated for the first time with real TerraSAR-X data and its performance is compared to state-of-the-art BAQ algorithms. The presented analyses demonstrate the improvements of the new TOPS imaging mode as well as the new FD-BAQ data compression algorithm for SAR image quality in general and in particular for Sentinel-1

Topography dependent motion compensation for repeat-pass interferometric SAR systems

This letter presents a new motion compensation algorithm to process airborne interferometric repeat-pass synthetic aperture radar (SAR) data. It accommodates topography variations during SAR data processing, using an external digital elevation model. The proposed approach avoids phase artifacts, azimuth coregistration errors, and impulse response degradation, which usually appear due to the assumption of a constant reference height during motion compensation. It accurately modifies phase history of all targets before azimuth compression, resulting in an enhanced image quality. Airborne L-band repeat-pass interferometric data of the German Aerospace Center experimental airborne SAR (E-SAR) is used to validate the algorithm.Peer Reviewe

Refined estimation of time-varying baseline errors in airborne SAR interferometry

The processing of airborne synthetic aperture radar (SAR) data requires a precise compensation of the deviations of the platform movement from a straight line. This is usually carried out by recording the trajectory with a high-precision navigation system and correcting them during SAR focusing. However, due to the lack of accuracy in current navigation systems, residual motion errors persist in the images. Such residual motion errors are mainly noticeable in repeat-pass systems, where they are causing time-varying baseline errors, visible as artefacts in the derived phase maps. In this letter, a refined method for the estimation of time-varying baseline errors is presented. An improved multisquint processing approach is used for obtaining robust estimates of higher order baseline errors over the entire scene, even if parts of the scene are heavily decorrelated. In a subsequent step, the proposed method incorporates an external digital elevation model for detection of linear and constant components of the baseline error along azimuth. Calibration targets in the scene are not necessary.Peer Reviewe

Monitoring the Petermann Ice Island with TanDEM-X

This paper presents the processing of TanDEM-X acquisitions for the monitoring of the topography of the Petermann ice island. In this particular case the area under study is continuously moving and the acquisition geometry is changing, so the processing of the iceberg’s DEMs is challenging and additional effects are to be considered. The SAR processing chain used is presented and the results obtained summarized, showing the effects and limitations observed during the process

Interpolation-free Coregistration and Phase-Correction of Airborne SAR Interferograms

This letter discusses the detection and correction of residual motion errors that appear in airborne synthetic aperture radar (SAR) interferograms due to the lack of precision in the navigation system. As it is shown, the effect of this lack of precision is twofold: azimuth registration errors and phase azimuth undulations. Up to now, the correction of the former was carried out by estimating the registration error and interpolating, while the latter was based on the estimation of the phase azimuth undulations to compensate the phase of the computed interferogram. In this letter, a new correction method is proposed, which avoids the interpolation step and corrects at the same time the azimuth phase undulations. Additionally, the spectral diversity technique, used to estimate registration errors, is critically analyzed. Airborne L-band repeat-pass interferometric data of the German Aerospace Center (DLR) experimental airborne SAR is used to validate the metho