Dr. Ioannis Ioannou Profile

Dr. Ioannis Ioannou

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Publications (16)

Proceedings Article | 14 October 2014 Paper

Remote estimation of in water constituents in coastal waters using neural networks

Ioannis Ioannou, Alexander Gilerson, Michael Ondrusek, Soe Hlaing, Robert Foster, Ahmed El-Habashi, Kaveh Bastani, Samir Ahmed

Proceedings Volume 9240, 92400T (2014) https://doi.org/10.1117/12.2067772

KEYWORDS: Absorption, Water, Neural networks, Satellites, Algorithm development, Data modeling, Computer simulations, Backscatter, MODIS, Atmospheric corrections

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Remote estimations of oceanic constituents from optical reflectance spectra in coastal waters are challenging because of the complexity of the water composition as well as difficulties in estimation of water leaving radiance in several bands possibly due to inadequacy of current atmospheric correction schemes. This work focuses on development of a multiband inversion algorithm that combines remote sensing reflectance measurements at several wavelengths in the blue, green and red for retrievals of the absorption coefficients of phytoplankton, color dissolved organic matter and nonalgal particulates at 443nm as well as the particulate backscatter coefficient at 443nm. The algorithm was developed, using neural networks (NN), and was designed to use as input measurements on ocean color bands matching those of the Visible Infrared Imaging Radiometer Suite (VIIRS). The NN is trained on a simulated data set generated through a biooptical model for a broad range of typical coastal water parameters. The NN was evaluated using several statistical indicators, initially on the simulated data-set, as well as on field data from the NASA bio-Optical Marine Algorithm Data set, NOMAD, and data from our own field campaigns in the Chesapeake Bay which represent well the range of water optical properties as well as chlorophyll concentrations in coastal regions. The algorithm was also finally applied on a satellite - in situ databases that were assembled for the Chesapeake Bay region using MODIS and VIIRS satellite data. These databases were created using in-situ chlorophyll concentrations routinely measured in different locations throughout Chesapeake Bay and satellite reflectance overpass data that coexist in time with these in-situ measurements. NN application on this data-sets suggests that the blue (412 and 443nm) satellite bands are erroneous. The NN which was assessed for retrievals from VIIRS using only the 486, 551 and 671 bands showed that retrievals that omitted the 671 nm band was the most effective, possibly indicating an inaccuracy in the VIIRS 671 band that needs to be further investigated.

Proceedings Article | 23 May 2014 Paper

Algorithms for the remote estimation of chlorophyll-a in the Chesapeake Bay

I. Ioannou, A. Gilerson, M. Ondrusek, Robert Foster, Ahmed El-Habashi, K. Bastani, S. Ahmed

Proceedings Volume 9111, 911118 (2014) https://doi.org/10.1117/12.2053753

KEYWORDS: Near infrared, Algorithm development, Neural networks, Absorption, Evolutionary algorithms, Satellites, Sensors, Reflectivity, Data modeling, MODIS

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Proceedings Article | 5 August 2013 Paper

Neural network approach to separate the non-algal absorption coefficient into dissolved and particulate

Ioannis Ioannou, Robert Foster, Alex Gilerson, Sam Ahmed

Proceedings Volume 8795, 87951N (2013) https://doi.org/10.1117/12.2028379

KEYWORDS: Absorption, Neural networks, Remote sensing, Reflectivity, Satellites, MODIS, Algorithm development, Sensors, Visible radiation, Water

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Proceedings Article | 3 June 2013 Paper

Neural network approach for the derivation of chlorophyll concentration from ocean color

Ioannis Ioannou, Robert Foster, Alex Gilerson, Barry Gross, Fred Moshary, Sam Ahmed

Proceedings Volume 8724, 87240P (2013) https://doi.org/10.1117/12.2018143

KEYWORDS: MODIS, Reflectivity, Water, Neural networks, Algorithm development, Absorption, Satellites, Remote sensing, Ocean optics, Data modeling

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Proceedings Article | 3 June 2013 Paper

Evaluation of VIIRS ocean color data using measurements from the AERONET-OC sites

Samir Ahmed, Alex Gilerson, Soe Hlaing, Ioannis Ioannou, Menghua Wang, Alan Weidemann, Robert Arnone

Proceedings Volume 8724, 87240L (2013) https://doi.org/10.1117/12.2017756

KEYWORDS: MODIS, Satellites, Aerosols, Sensors, Calibration, Statistical analysis, Atmospheric corrections, Avalanche photodetectors, Data processing, Ocean optics

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Proceedings Article | 10 September 2011 Paper

Exploring the relation between polarized light fields and physical-optical characteristics of the ocean for remote sensing applications

Amir Ibrahim, Tristan Harmel, Alberto Tonizzo, Ioannis Ioannou, Alex Gilerson, Samir Ahmed

Proceedings Volume 8160, 81600H (2011) https://doi.org/10.1117/12.894113

KEYWORDS: Particles, Scattering, Water, Polarization, Sun, Refractive index, Signal attenuation, Light scattering, Absorption, Optical properties

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Proceedings Article | 18 October 2010 Paper

Sensitivity of the above water polarized reflectance to the water composition

A. Tonizzo, T. Harmel, A. Ibrahim, S. Hlaing, I. Ioannou, A. Gilerson, J. Chowdhary, B. Gross, F. Moshary, S. Ahmed

Proceedings Volume 7825, 78250F (2010) https://doi.org/10.1117/12.865510

KEYWORDS: Sensors, Radiative transfer, Polarization, Absorption, Scattering, Water, Reflectivity, Atmospheric modeling, Contamination, Satellites

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Estimating the Stokes vector components of the polarized water radiance from above water measurements is a challenging task, mainly because of their small magnitude and the strong contamination by the sky light reflected on the sea surface. Consequently, in most applications the Stokes vector components are considered equal to zero except of I, the total reflectance. In this study, both below and above water measurements are used to assess the feasibility of such retrievals and their use to determine the water composition. In-water inherent optical properties (IOPs) were measured with commercially available instrumentation. In addition, in-water polarization characteristics were measured by our multi-angular hyperspectral sensor which provided the Stokes components for a scattering angles range of the 0-180° and a full spectral range between 400 and 750 nm. Second, a customized HyperSAS (Satlantic) instrument is used from the coastal platform in Long Island Sound, NY (LISCO) acquiring above water measurements. That instrumentation includes, in the standard configuration, two hyperspectral radiance sensors for measuring upwelling and sky radiances and one irradiance sensor for measuring downwelling irradiance. In our installation, HyperSAS capabilities were augmented by adding two radiance sensors having two polarizers oriented at 0 and 45°, with respect to a reference axis ("HyperSAS-POL"). An ad hoc procedure, which included measurements and radiative transfer computations, has been developed enabling to estimate the contribution of the sky glint and subtract it from the signal directly measured by HyperSAS-POL. As a result, the retrieved spectral shape of the underwater degree of polarization is consistent with what obtained from in situ underwater measurements and depends on the IOPs of the ocean itself. In addition, the demonstrated correctness of this polarized measurements from LISCO site enable us to provide continuous time series from the beginning of June 2010.

Proceedings Article | 7 October 2010 Paper

Validation of ocean color satellite sensors using coastal observational platform in Long Island Sound

Soe Hlaing, Tristan Harmel, Amir Ibrahim, Ioannis Ioannou, Alberto Tonizzo, Alexander Gilerson, Samir Ahmed

Proceedings Volume 7825, 782504 (2010) https://doi.org/10.1117/12.865123

KEYWORDS: Satellites, Calibration, MODIS, Sensors, Avalanche photodetectors, Remote sensing, Radiometry, Atmospheric corrections, Ocean optics, Hyperspectral imaging

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Proceedings Article | 10 September 2009 Paper

New algorithm for MODIS chlorophyll fluorescence height retrieval: performance and comparison with the current product

I. Ioannou, J. Zhou, A. Gilerson, B. Gross, F. Moshary, S. Ahmed

Proceedings Volume 7473, 747309 (2009) https://doi.org/10.1117/12.830630

KEYWORDS: Luminescence, MODIS, Absorption, Reflectivity, Sensors, Scattering, Satellites, Signal detection, Computer simulations, Algorithm development

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Proceedings Article | 19 August 2009 Paper

Evaluation of solar stimulated CDOM fluorescence and its impact on the closure of remote sensing reflectance

J. Zhou, A. Tonizzo, I. Ioannou, S. Hlaing, A. Gilerson, B. Gross, F. Moshary, S. Ahmed

Proceedings Volume 7459, 74590B (2009) https://doi.org/10.1117/12.825374

KEYWORDS: Luminescence, Reflectivity, Absorption, Remote sensing, Backscatter, Quantum efficiency, Optical properties, Fluorescence spectroscopy, Spectroscopy, Radiative transfer

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Proceedings Article | 19 August 2009 Paper

Inversion of inherent optical properties of water using artificial neural network techniques for coastal water

I. Ioannou, J. Zhou, A. Gilerson, B. Gross, F. Moshary, S. Ahmed

Proceedings Volume 7459, 745909 (2009) https://doi.org/10.1117/12.825386

KEYWORDS: Absorption, Data modeling, Water, Backscatter, Ultraviolet radiation, Neural networks, Reflectivity, Optical properties, Computer simulations, Remote sensing

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Proceedings Article | 13 October 2008 Paper

Untangling the make-up of the NIR reflectance peak in coastal waters and its impact on remote sensing retrievals of [Chl] and fluorescence height algorithms

S. Ahmed, A. Gilerson, J. Zhou, R. Dyer, S. Hlaing, I. Ioannou, B. Gross, F. Moshary

Proceedings Volume 7105, 710508 (2008) https://doi.org/10.1117/12.800378

KEYWORDS: Luminescence, Absorption, Reflectivity, Near infrared, Quantum efficiency, Atmospheric corrections, Short wave infrared radiation, Lithium, Satellites, Backscatter

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Proceedings Article | 8 October 2007 Paper

Impact of scattering and absorption of photosynthetic pigments on fluorescence retrieval algorithms for coastal waters

S. Ahmed, A. Gilerson, J. Zhou, S. Hlaing, I. Ioannou, W. Jerez, B. Gross, F. Moshary

Proceedings Volume 6743, 674307 (2007) https://doi.org/10.1117/12.737431

KEYWORDS: Luminescence, Absorption, Reflectivity, MODIS, Minerals, Computer simulations, Satellites, Signal attenuation, Quantum efficiency, Near infrared

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Fluorescence Line Height (FLH) algorithms are effective for fluorescence retrieval in the open ocean where elastic reflectance in the fluorescence zone does not deviate much from the baseline. In coastal waters, FLH algorithms are significantly complicated by the overlap of the fluorescence and elastic reflectance peaks. To test accuracy of MODIS, MERIS and other FLH algorithms, we compared numerical simulations using an extensive synthetic database suitable for case II waters, with results of extensive field measurements of reflectance, absorption and attenuation spectra by us in the Chesapeake Bay, as well as satellite FLH data from several areas that typically show low correlation between [Chl] and FLH. Our synthetic datasets were created using the HYDROLIGHT radiative transfer code with IOP's connected to parameterized microphysical models in accordance with procedures used to generate the IOCCG dataset, but with some added improvements. These included higher (1 nm) spectral resolution, a wider range of parameters typical for coastal waters, including chlorophyll specific absorptions with significant variations in spectral shapes and magnitude. HYDROLIGHT simulations of elastic reflectance using measured attenuation/extinction spectra followed by subtraction from measured reflectance, permitted retrieval of the fluorescence contribution to the latter, for comparisons with the data set simulations. We find relatively small fluorescence contributions to surface reflectance for mineral concentrations > 5 mg/l because of strong attenuation in the excitation zone and enhanced elastic reflectance making fluorescence detection unrealistic. For lower mineral concentrations, we find that some combinations of NIR observation bands permit reasonably good FLH retrievals in conditions where specific absorption spectral variation is not very high, and that application of multi-spectral algorithms can be more efficient for the retrieval of fluorescence contributions in coastal areas.

Proceedings Article | 5 October 2007 Paper

Fluorescence contribution to reflectance spectra for a variety of coastal waters

A. Gilerson, J. Zhou, S. Hlaing, I. Ioannou, R. Amin, B. Gross, F. Moshary, S. Ahmed

Proceedings Volume 6680, 66800C (2007) https://doi.org/10.1117/12.731663

KEYWORDS: Luminescence, Absorption, Reflectivity, Minerals, Near infrared, Quantum efficiency, Scattering, Signal attenuation, Particles, Backscatter

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Proceedings Article | 25 September 2007 Paper

Continuous spectral measurement of backscattering in sea water

J. Zhou, A. Gilerson, I. Ioannou, B. Gross, F. Moshary, S. Ahmed

Proceedings Volume 6755, 67550J (2007) https://doi.org/10.1117/12.731642

KEYWORDS: Backscatter, Scattering, Luminescence, Light scattering, Optical filters, Absorption, Signal detection, Light sources, Lamps, Mie scattering

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Proceedings Article | 28 November 2006 Paper

Evaluation of the impact of backscatter spectral characteristics on Chl retrievals in coastal waters

S. Ahmed, A. Gilerson, J. Zhou, J. Chowdhary, I. Ioannou, R. Amin, B. Gross, F. Moshary

Proceedings Volume 6406, 64060A (2006) https://doi.org/10.1117/12.694177

KEYWORDS: Backscatter, Reflectivity, Absorption, Scattering, Near infrared, Signal attenuation, Particles, Water, Luminescence, Minerals

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Showing 5 of 16 publications

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