SAR imaging and detection of partially coherent targets

A synthetic aperture radar (SAR) achieves a high azimuth resolution by illuminating targets with multiple pulses and using the Doppler history to synthesize a large antenna. When combining the pulses, it is normally assumed that the targets are stationary, and that their reflectivity is independent of time. The topic of this thesis is the processing of SAR images where the the targets have a time-dependent reflectivity. One can imagine, for instance, a ship rolling in a rough sea. One possible way of processing such targets is described by R. Keith Raney. The goal of this thesis is to provide a well structured introduction into Raney's formalism on partially coherent targets, and to investigate a focusing strategy for scenes where the targets have different coherence times. The image formation processes of a synthetic aperture radar is thoroughly discussed, and a one-dimensional model of the azimuth dimension is introduced. Raney's formalism is compared to this model and found to be formally correct. A partially coherent point target is simulated, and Raney's formalism is tested for the purpose of target detection in the presence of scene partial coherence. It is shown that the whole system, including partial coherence in both scene and processor, behaves as a Gaussian low-pass filter weighted by the scene autocorrelation function and the processor coherence function

Early identification of mushy Halibut syndrome with hyperspectral image analysis

Mushy Halibut Syndrome (MHS) is a condition that appears in Greenland halibut and manifests itself as abnormally opaque, flaccid and jelly-like flesh. Fish affected by this syndrome show poor meat quality, which results in negative consequences for the fish industry. The research community has not carefully investigated this condition, nor novel technologies for MHS detection have been proposed. In this research work, we propose using hyperspectral imaging to detect MHS. After collecting a dataset of hyperspectral images of halibut affected by MHS, two different goals were targeted. Firstly, the estimation of the chemical composition of the samples (specifically fat and water content) from their spectral data by using constrained spectral unmixing. Secondly, supervised classification using partial least squares discriminant analysis (PLS-DA) was evaluated to identify specimens affected by MHS. The outcomes of our study suggest that the prediction of fat from the spectral data is possible, but the prediction of the water content was not found to be accurate. However, the detection of MHS using PLS-DA was precise for hyperspectral images from both fillets and whole fish, with lower bounds of 75% and 83% for precision and recall, respectively. Our findings suggest hyperspectral imaging as a suitable technology for the early screening of MHS.Early identification of mushy Halibut syndrome with hyperspectral image analysispublishedVersio

Early identification of mushy Halibut syndrome with hyperspectral image analysis

Mushy Halibut Syndrome (MHS) is a condition that appears in Greenland halibut and manifests itself as abnormally opaque, flaccid and jelly-like flesh. Fish affected by this syndrome show poor meat quality, which results in negative consequences for the fish industry. The research community has not carefully investigated this condition, nor novel technologies for MHS detection have been proposed. In this research work, we propose using hyperspectral imaging to detect MHS. After collecting a dataset of hyperspectral images of halibut affected by MHS, two different goals were targeted. Firstly, the estimation of the chemical composition of the samples (specifically fat and water content) from their spectral data by using constrained spectral unmixing. Secondly, supervised classification using partial least squares discriminant analysis (PLS-DA) was evaluated to identify specimens affected by MHS. The outcomes of our study suggest that the prediction of fat from the spectral data is possible, but the prediction of the water content was not found to be accurate. However, the detection of MHS using PLS-DA was precise for hyperspectral images from both fillets and whole fish, with lower bounds of 75% and 83% for precision and recall, respectively. Our findings suggest hyperspectral imaging as a suitable technology for the early screening of MHS.Early identification of mushy Halibut syndrome with hyperspectral image analysispublishedVersio

Assessing the potential of fluorescence as a monitoring tool for reproductive tissue in selected macroalgae species

Biofluorescence in certain seaweed species has been studied in association with their respective chlorophyll type and concentration. However, there is a paucity of information on the biofluorescent signature of macroalgal species at different life stages. Here we document that hyperspectral imaging differentiates between the fluorescent signatures of 5 macroalgal species (Ascophyllum nodosum, Fucus vesiculosus, Laminaria digitata, Palmaria palmata, and Saccharina latissima) collected from Tromsø, northern Norway (69-70 °N). Non-reproductive (NR) blades were collected for all species and reproductively mature blades (R) with sori were collected for three species. Hyperspectral imaging of collected blades was conducted under excitation lighting (~445 nm). We further assessed whether biofluorescence is reflected in the reproductive phenology of three selected species, L. digitata, P. palmata, and S. latissima. The spectral radiance of fluorescence emissions was found to be consistently different between R and NR blades. The greatest difference between R and NR blades was between the rhodophyte P. palmata (0.0075 W nm-1sr-1m-2 at 725 nm) followed by the phaeophytes L. digitata (0.03 W nm-1sr-1m-2 at 730-740 nm) and S. latissima (0.00225 W nm-1sr-1m-2 at 735-745 nm). Biofluorescence monitoring with hyperspectral imaging should be considered for further applicability in commercial seaweed operations.publishedVersio

Hidden in plain sight: hyperspectral documentation of complex biofluorescence produced by the green sea urchin (Strongylocentrotus droebachiensis)

Biofluorescence in echinoderms is largely unexplored, and even though the green sea urchin Strongylocentrotus droebachiensis is a well-studied species, the presence and/or function of fluorescence remains very poorly understood. Hyperspectral imaging was conducted on adult sea urchins (N = 380) while fluorospectrometric analysis was conducted on sea urchin coelomic fluid (N = 30). Fluorescence was documented in both the spines and coelomic fluid of S. droebachiensis. Intact spines exhibited a low intensity green emission (∼550–600 nm), while broken spines averaged a high emission peak in the green spectrum (∼580 nm). Sea urchins produce a red exudate with a pronounced emission peak (∼680 nm) with a shoulder peak (∼730 nm). The sampled coelomic fluid exhibited high variability, with a majority exhibiting a low-level green fluorescence while pronounced emission peaks (N = 5) were found in the red spectrum (∼680 nm). The complex fluorescence produced by S. droebachiensis warrants further investigation on its applicability for monitoring welfare of sea urchins in aquaculture facilities.publishedVersio

Perspective Chapter: Hyperspectral Imaging for the Analysis of Seafood

Hyperspectral imaging technology is able to provide useful information about the interaction between electromagnetic radiation and matter. This information makes possible chemical characterization of materials in a non-invasive manner. For this reason, the technology has been of great interest for the food industry in recent decades. In this book chapter, we provide a survey of the current status of the use of hyperspectral technology for seafood evaluation. First, we provide a brief description of the optical properties of tissue and an introduction to the instrumentation used to capture these images. Then, we survey the main applications of hyperspectral imaging in the seafood industry, including the quantification of different chemical components, the estimation of freshness, the quality assessment of seafood products, and the detection of nematodes, among others. Finally, we provide a discussion about the current state of the art and the upcoming challenges for the application of this technology in the seafood industry

Effect of the T90-codend on the catch quality of cod (Gadus morhua) compared to the conventional codend configuration in the Barents Sea bottom trawl fishery

The aim of this study was to compare the catch quality of Northeast Atlantic cod (Gadus morhua) in the Barents Sea bottom trawl fishery caught using the conventional configuration (a sorting grid followed by a diamond mesh (T0) codend) and a T90° turned mesh codend (T90) without a grid. Twenty hauls were conducted, consisting of 10 hauls with the conventional configuration and 10 hauls with the T90-codend. The catch quality was assessed using the catch-damages-index (CDI) and a newly developed method using VIS/NIR hyperspectral imaging to estimate the residual blood abundances in the fish muscle. The probability of obtaining fish with no damage was 23.4% (CI: 16.3–31.1%) for cod captured by the conventional configuration, and 21.2% (CI: 15.4–27.2%) for cod captured by the T90-codend. The average blood abundance (in arbitrary unit) was 0.86 (CI: 0.85–0.87) for cod captured by the conventional configuration and 0.88 (CI: 0.87–0.88) for cod captured by the T90-codend. Catch quality of the hauls obtained using the two gears did not differ significantly in terms of catch damage or residual blood levels in the cod. Hence, this study demonstrated that T90-codends do not compromise catch quality compared to regular diamond meshed codends.publishedVersio

Raman spectroscopy and NIR hyperspectral imaging for in-line estimation of fatty acid features in salmon fillets

Raman spectroscopy was compared with near infrared (NIR) hyperspectral imaging for determination of fat composition (%EPA + DHA) in salmon fillets at short exposure times. Fillets were measured in movement for both methods. Salmon were acquired from several different farming locations in Norway with different feeding regimes, representing a realistic variation of salmon in the market. For Raman, we investigated three manual scanning strategies; i) line scan of loin, ii) line scan of belly and iii) sinusoidal scan of belly at exposure times of 2s and 4s. NIR images were acquired while the fillets moved on a conveyor belt at 40 cm/s, which corresponds to an acquisition time of 1s for a 40 cm long fillet. For NIR images, three different regions of interest (ROI) were investigated including the i) whole fillet, ii) belly segment, and iii) loin segment. For both Raman and NIR measurements, we investigated an untrimmed and trimmed version of the fillets, both relevant for industrial in-line evaluation. For the trimmed fillets, a fat rich deposition layer in the belly was removed. The %EPA + DHA models were validated by cross validation (N = 51) and using an independent test set (N = 20) which was acquired in a different season. Both Raman and NIR showed promising results and high performances in the cross validation, with R2CV = 0.96 for Raman at 2s exposure and R2CV = 0.97 for NIR. High performances were obtained also for the test set, but while Raman had low and stable biases for the test set, the biases were high and varied for the NIR measurements. Analysis of variance on the squared test set residuals showed that performance for Raman measurements were significantly higher than NIR at 1% significance level (p = 0.000013) when slope-and-bias errors were not corrected, but not significant when residuals were slope-and-bias corrected (p = 0.28). This indicated that NIR was more sensitive to matrix effects. For Raman, signal-to-noise ratio was the main limitation and there were indications that Raman was close to a critical sample exposure time at the 2s signal accumulation.publishedVersio

Teknologi for automatisk sortering av tørrfisk

Tørking av fisk ute på hjell er en tradisjonell og mye brukt metode for konservering av fisk. Kvaliteten på sluttproduktet blir i stor grad avhengig av værforhold under tørking og kvaliteten på råstoffet som henges. Når fisken tørkes ute blir den utsatt for variasjon i temperatur, vind, sol og fuktighet. Til sammen gir dette en tørket og modnet fisk som har karakteristisk lukt, smak og konsistens. Ute-tørking innebærer også at en del fisk ikke får optimale forhold gjennom tørking, for å oppnå ønsket utseende, konsistens, lukt og smak. Kvalitetsfeil som kan forekomme på en ferdig tørket tørrfisk er frostskader, blodfeil, spalting i muskel, mucoso makk/fluelarver på innsiden av fisken, og muggvekst på skinnet. Å kvalitetsvurdere tørrfisk, vraking, er en tidkrevende prosess som krever opplæring og erfaring. Kvalitetsfeil på tørrfisk kan være vanskelig å oppdage, og feilene vises ofte først når fisken er ferdig sortert og blir vannet ut. I praksis betyr det at feilene først registreres hos bedrifter og kunder som videreforedler fisken. Tørrfisknæringen har etterspurt teknologi for å automatisere kvalitetsvurdering på tvers av kvalitetsgrupper med fokus på blod i fiskemuskel, frostskader, mucoso, og grunnleggende kvalitet. Prosjektet har hatt som hovedmål å utvikle en rask og ikke destruktiv metode for automatisk kvalitetssortering av tørrfisk. Fokus i gjennomføring har vært på kvalitetsfeilene blod i muskel og frostskader. Måling på tørrfisk er gjort ved bruk av Maritech Eye, hyperspektral avbildning, og referansen for disse målingene er sensorisk kvalitetsvurdering av både tørrfisk og utvannet tørrfisk. Det er utviklet modeller basert på maskinlæring som gjør det mulig å finne kvalitetsfeil i tørrfisken. Resultatene så langt viser at dette fungerer best for påvisning av frostskade i tørrfisk. Det fungerer delvis for påvisning av blodfeil i tørrfisk, men da med større feilmargin. Videre arbeid for å utvikle metodikk for automatisk påvisning av kvalitetsfeil i tørrfisk bør fokusere på å forbedre modellene for påvisning av blodfeil i muskelen. Det er også gjort en kost-nytte analyse for bruken av et slik verktøy i tørrfisknæringen. Resultatet av analysen indikerer at dette kan være lønnsomt også for en relativt lav grad av reduserte personalkostnader knyttet til vraking.Teknologi for automatisk sortering av tørrfiskpublishedVersio

Applications of hyperspectral imaging for documenting smoltification status and welfare in Atlantic salmon

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