Hyperspectral Remote Sensing Applied to Shallow Coastal Waters

A shallow water reflectance model was developed for application to optical remote sensing in highly diverse and complex coastal environments. A numerical inversion scheme, based on analytical parameterisation, was applied to airborne hyperspectral imagery collected over two regions of the Western Australian coastline; Jurien Bay and the Ningaloo Marine Park. Detailed maps of water quality, water depth and benthic cover classification were derived with a high degree of accuracy as compared to ground truth data

Intercomparison of shallow water bathymetry, hydro-optics, and benthos mapping techniques in Australian and Caribbean coastal environments

Science, resource management, and defense need algorithms capable of using airborne or satellite imagery to accurately map bathymetry, water quality, and substrate composition in optically shallow waters. Although a variety of inversion algorithms are available, there has been limited assessment of performance and no work has been published comparing their accuracy and efficiency. This paper compares the absolute and relative accuracies and computational efficiencies of one empirical and five radiative-transfer-based published approaches applied to coastal sites at Lee Stocking Island in the Bahamas and Moreton Bay in eastern Australia. These sites have published airborne hyperspectral data and field data. The assessment showed that (1) radiative-transfer-based methods were more accurate than the empirical approach for bathymetric retrieval, and the accuracies and processing times were inversely related to the complexity of the models used; (2) all inversion methods provided moderately accurate retrievals of bathymetry, water column inherent optical properties, and benthic reflectance in waters less than 13 m deep with homogeneous to heterogeneous benthic/substrate covers; (3) slightly higher accuracy retrievals were obtained from locally parameterized methods; and (4) no method compared here can be considered optimal for all situations. The results provide a guide to the conditions where each approach may be used (available image and field data and processing capability). A re-analysis of these same or additional sites with satellite hyperspectral data with lower spatial and radiometric resolution, but higher temporal resolution would be instructive to establish guidelines for repeatable regional to global scale shallow water mapping approaches

Shallow water substrate mapping using hyperspectral remote sensing

During April 2004 the airborne hyperspectral sensor, HyMap, collected data over a shallow coastalregion of Western Australia. These data were processed by inversion of a semi-analytical shallow wateroptical model to classify the substrate. Inputs to the optical model include water column constituentspecific inherent optical properties (SIOPs), view and illumination geometry, surface condition (basedon wind speed) and normalised reflectance spectra of substrate types. A sub-scene of the HyMap datacovering approximately 4 km2 was processed such that each 3!3 m2 pixel was classed as sand,seagrass, brown algae or various mixtures of these three components. Coincident video data werecollected and used to estimate substrate types. We present comparisons of the habitat classificationsdetermined by these two methods and show that the percentage validation of the remotely sensedhabitat map may be optimised by selection of appropriate optical model parameters. The optical modelwas able to retrieve classes for approximately 80% of all pixels in the scene, with validation percentagesof approximately 50% for sand and seagrass classification, and 90% for brown algae classification. Thesemi-analytical model inversion approach to classification can be expected to be applied to any shallowwater region where substrate reflectance spectra and SIOPs are known or can be inferred

Uncertainty assessment of unattended above-water radiometric data collection from research vessels with the Dynamic Above-water Radiance (L) and Irradiance (E) Collector (DALEC)

International audienceWe used above-and below-water radiometry measurements collected during a research voyage in the eastern Indian Ocean to assess uncertainties in deriving the remote sensing reflectance, R rs , from unattended above-water radiometric data collection with the In-Situ Marine Optics Pty. Ltd. (IMO) Dynamic Above-water Radiance (L) and Irradiance (E) Collector (DALEC). To achieve this, the R rs values derived from using the latest version of this hyperspectral radiometer were compared to values obtained from two in-water profiling radiometer systems of rather general use in the ocean optics research community, i.e., the Biospherical Instruments Inc. Compact Optical Profiling System (C-OPS) and the Seabird HyperPro II. Our results show that unattended, carefully quality-controlled, DALEC measurements provide R rs for wavelengths < 600 nm that match those derived from the in-water systems with no bias and a dispersion of about 8%, provided that the appropriate technique is used to quantify the contribution of sky light reflection to the measured signal. The dispersion is larger (25-50%) for red bands, which is expected for clear oligotrophic waters as encountered during the voyage, where ∼2 10 −5 < R rs < ∼2 10 −4 sr −1. For comparison, the two in-water systems provided R rs in agreement within 4% for wavelengths < 600 nm

Hyperspectral remote sensing of the Ningaloo Reef: Data collection, processing, validation and applications in monitoring one of the world's largest, most diverse and pristine tropical coral reef ecosystems

Underway physical and radiometric data were captured within the Ningaloo Marine Park. Three underway transects were conducted coincident with HyMap overpasses. Local mode MISR data and ancillary aerosol and meteorological observations complete the validation se

Venous thromboembolism risk and prophylaxis in hospitalised medically ill patients The ENDORSE Global Survey

Limited data are available regarding the risk for venous thromboembolism (VIE) and VIE prophylaxis use in hospitalised medically ill patients. We analysed data from the global ENDORSE survey to evaluate VTE risk and prophylaxis use in this population according to diagnosis, baseline characteristics, and country. Data on patient characteristics, VIE risk, and prophylaxis use were abstracted from hospital charts. VTE risk and prophylaxis use were evaluated according to the 2004 American College of Chest Physicians (ACCP) guidelines. Multivariable analysis was performed to identify factors associated with use of ACCP-recommended prophylaxis. Data were evaluated for 37,356 hospitalised medical patients across 32 countries. VIE risk varied according to medical diagnosis, from 31.2% of patients with gastrointestinal/hepatobiliary diseases to 100% of patients with acute heart failure, active noninfectious respiratory disease, or pulmonary infection (global rate, 41.5%). Among those at risk for VTE, ACCP-recommended prophylaxis was used in 24.4% haemorrhagic stroke patients and 40-45% of cardiopulmonary disease patients (global rate, 39.5%). Large differences in prophylaxis use were observed among countries. Markers of disease severity, including central venous catheters, mechanical ventilation, and admission to intensive care units, were strongly associated with use of ACCP-recommended prophylaxis. In conclusion, VIE risk varies according to medical diagnosis. Less than 40% of at-risk hospitalised medical patients receive ACCP-recommended prophylaxis. Prophylaxis use appears to be associated with disease severity rather than medical diagnosis. These data support the necessity to improve implementation of available guidelines for evaluating VIE risk and providing prophylaxis to hospitalised medical patients

Venous Thromboembolism Risk and Prophylaxis in the Acute Care Hospital Setting (ENDORSE Survey) Findings in Surgical Patients

Objective: To evaluate venous thromboembolism (VTE) risk in patients who underwent a major operation, including the use of, and factors influencing, American College of Chest Physicians-recommended types of VTE prophylaxis