Complete Tri-Axis Magnetometer Calibration with a Gyro Auxiliary

Magnetometers combined with inertial sensors are widely used for orientation estimation, and calibrations are necessary to achieve high accuracy. This paper presents a complete tri-axis magnetometer calibration algorithm with a gyro auxiliary. The magnetic distortions and sensor errors, including the misalignment error between the magnetometer and assembled platform, are compensated after calibration. With the gyro auxiliary, the magnetometer linear interpolation outputs are calculated, and the error parameters are evaluated under linear operations of magnetometer interpolation outputs. The simulation and experiment are performed to illustrate the efficiency of the algorithm. After calibration, the heading errors calculated by magnetometers are reduced to 0.5° (1σ). This calibration algorithm can also be applied to tri-axis accelerometers whose error model is similar to tri-axis magnetometers

Metodi strumentali innovativi a supporto della valutazione del paziente con emianopsia

L’emianopsia è un deficit centrale della visione che consiste nella perdita di una porzione di campo visivo al quale si associa una disorganizzazione dei movimenti oculari. Ciò risulta in una limitazione dell’autonomia nello svolgimento nelle attività quotidiane, come il muoversi in ambienti con ostacoli, che è solitamente valutata con questionari autosomministrati. Il trattamento riabilitativo che permette un recupero funzionale è di tipo compensativo, atto a rendere più efficaci le strategie oculomotorie. Questo elaborato è uno studio esplorativo su due possibili metodiche atte a valutare l’impatto funzionale dell’emianopsia: nella prima i partecipanti svolgono un compito che prevede movimenti saccadici e, sfruttando un’elaborazione automatica del segnale oculomotorio da eye-tracker, vengono estratti parametri d’interesse clinico. Nel secondo esperimento si è utilizzato un set-up ecologico che prevede il cammino con aggiramento di ostacoli verticali e sono stati estratti potenziali indicatori clinici da sensori magneto-inerziali posizionati sui piedi ed in fronte. Sono stati estratti parametri dall’orientamento della testa, dalla traiettoria messa in atto e quelli spazio-temporali del passo. In entrambi gli studi hanno partecipato emianoptici e soggetti sani, tra cui si è controllato quali parametri permettevano di distinguere le due popolazioni. Inoltre, si è valutato qualitativamente se gli indicatori potessero avere ricadute cliniche con acquisizioni ripetute pre e post-trattamento. Nel primo studio sono risultati in grado di discriminare tra i due gruppi l’accuratezza nella risposta, nella saccade di ritorno sia quando eccessiva che quando troppo ridotta ed il numero di correzioni. Nel secondo sono risultati significativamente diversi la velocità e la lunghezza del passo. I risultati preliminari di questa ricerca mettono in luce la potenzialità di questi strumenti per il loro utilizzo nella pratica clinica per la valutazione del paziente con emianopsia

Multi-scale movement of demersal fishes in Alaska

Thesis (Ph.D.) University of Alaska Fairbanks, 2019Information on the movement of migratory demersal fishes such as Pacific halibut, Pacific cod, and sablefish is needed for management of these valuable fisheries in Alaska, yet available methods such as conventional tagging are too coarse to provide detailed information on migration characteristics. In this dissertation, I present methods for characterizing seasonal and annual demersal fish movement at multiple scales in space and time using electronic archival and acoustic tags. In Chapter 1, acoustic telemetry and the Net Squared Displacement statistic were used to identify and characterize small-scale movement of adult female Pacific halibut during summer foraging in a Marine Protected Area (MPA). The dominant movement pattern was home range behavior at spatial scales of less than 1 km, but a more dispersive behavioral state was also observed. In Chapter 2, Pop-up Satellite Archival Tags (PSATs) and acoustic tags were deployed on adult female Pacific halibut to determine annual movement patterns relative to MPA boundaries. Based on observations of summer home range behavior, high rates of year-round MPA residency, migration timing that largely coincided with winter commercial fisheries closures, and the demonstrated ability of migratory fish to return to previously occupied summer foraging areas, the MPA is likely to be effective for protecting both resident and migrant Pacific halibut brood stock year-round. In Chapter 3, I adapted a Hidden Markov Model (HMM) originally developed for geolocation of Atlantic cod in the North Sea for use on demersal fishes in Alaska, where maximum daily depth is the most informative and reliable geolocation variable. Because depth is considerably more heterogeneous in many regions of Alaska compared to the North Sea, I used simulated trajectories to determine that the degree of bathymetry heterogeneity affected model performance for different combinations of likelihood specification methods and model grid sizes. In Chapter 4, I added a new geolocation variable, geomagnetic data, to the HMM in a small-scale case study. The results suggest that the addition of geomagnetic data could increase model performance over depth alone, but more research is needed to continue validation of the method over larger areas in Alaska. In general, the HMM is a flexible tool for characterizing movement at multiple spatial scales and its use is likely to enrich our knowledge about migratory demersal fish movement in Alaska. The methods developed in this dissertation can provide valuable insights into demersal fish spatial dynamics that will benefit fisheries management activities such as stock delineation, stock assessment, and design of space-time closures.Rasmuson Fisheries Research Center and the Pollock Conservation Cooperative Research CenterChapter 1: Characterizing Pacific halibut movement and habitat in a Marine Protected Area using net squared displacement analysis methods -- Chapter 2: Interannual site fidelity of Pacific halibut: potential utility of protected areas for management of a migratory demersal fish -- Chapter 3 Effect of study area bathymetric heterogeneity on parameterization and performance of a depth depth-based geolocation model for demersal fishes -- Chapter 4 Potential utility of geomagnetic data for geolocation of demersal fish in the North Pacific Ocean -- General conclusion -- References -- Appendix A: Geolocation of demersal fishes in the North Pacific Ocean: Hidden Markov model framework and data likelihood models