@conference{Karageorgis2019,

title = {The LEVECO project Bio-Optics experiment in the northwestern Levantine Sea: Preliminary results},

author = {A.P. Karageorgis and P.G. Drakopoulos and S. Chaikalis and A. Lagaria and N. Spyridakis and S. Psarra, , Proc. SPIE , 11174, (2019), },

url = {https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11174/2533658/The-LEVECO-project-bio-optics-experiment-in-the-northwestern-Levantine/10.1117/12.2533658.short},

doi = {https://doi.org/10.1117/12.2533658},

year  = {2019},

date = {2019-06-27},

volume = {11174},

publisher = {Proceedings of SPIE},

organization = {Seventh International Conference on Remote Sensing and Geoinformation of the Environment (RSCy2019)},

keywords = {backscatter, ocean optics, particles, reflectivity, remote sensing, sensors, signal attenuation},

pubstate = {published},

tppubtype = {conference}

}

@conference{Karageorgis2018b,

title = {LEVECO: Hydrology and bio-optics},

author = {A.P. Karageorgis and P.G. Drakopoulos and S. Chaikalis and A. Androni and A. Lagaria and I. Stavrakaki and N. Spyridakis and S. Psarra },

year  = {2018},

date = {2018-05-31},

address = {Ionian University, Corfu},

organization = {Proc. 12th Panhel. Symp. Oceanogr. & Fish.},

note = {30 May - 3 June},

keywords = {bio-optics, hydrology, optics},

pubstate = {published},

tppubtype = {conference}

}

@conference{Tsapanou2018,

title = {Remote sensing of suspended particulate matter, over a region of river influence; the case study of northeastern Aegean Sea},

author = {A. Tsapanou and P.G. Drakopoulos and E.Oikonomou and S.Poulos and G. Sylaios},

year  = {2018},

date = {2018-05-30},

address = {Ionian University, Corfu},

organization = {Proc. 12th Panhel. Symp. Oceanogr. & Fish.},

note = {30 May - 3 June},

keywords = {Aegean Sea, particles, river},

pubstate = {published},

tppubtype = {conference}

}

@conference{Karageorgis2018,

title = {Advancing ocean colour retrieval for the Hellenic Seas},

author = {A. Karageorgis and P.G. Drakopoulos and S. Iona and V. Kapsimalis and S. Psarra and S. Sofianos and N. Spyridakis and K. Topouzelis and V. Zervakis},

year  = {2018},

date = {2018-01-10},

booktitle = {Joint efforts of Research Institutes and Academia, Book of Abstracts},

pages = {35-36},

organization = {Hellenic Geological Society 1st meeting on Remote Sensing and Space Applications Committee of the Geological Society of Greece},

keywords = {Hellenic Seas, ocean colour, retrieval},

pubstate = {published},

tppubtype = {conference}

}

@conference{Papadopoulou2017,

title = {Determining the level of uncertainty between in situ and MODIS satellite-derived chlorophyll-α estimations in the optically complex North Aegean Sea waters},

author = {A. Papadopoulou and P.G. Drakopoulos and S. Psarra and A.P. Karageorgis and A. Lagaria and N. Spyridakis and Vassilis Zervakis},

url = {https://www.researchgate.net/publication/282824208_Estimating_chlorophyll_concentrations_in_the_optically_complex_waters_of_the_North_Aegean_Sea_from_field_and_satellite_ocean_colour_measurements},

year  = {2017},

date = {2017-05-15},

address = {Lisbon Portugal},

organization = {3rd International Ocean Colour Science meeting},

abstract = {In the Aegean Sea and Eastern Mediterranean there are large discrepancies between in situ and satellite ocean colour derived chlorophyll concentrations. The quantity that is monitored by ocean colour satellites and that can be used in the estimation of chlorophyll concentration is the remote sensing reflectance, defined as the ratio of the water leaving spectral radiance to the downwelling spectral irradiance. It can be determined in the field, with either above or in-water radiance and irradiance measurements. The complex optical properties of the North-East Aegean Sea, including radiance and irradiance, were studied during the AegeanMarTech project. Chlorophyll concentration estimates were derived from simultaneous above and in-water radiometric measurements. These were validated against chlorophyll concentration field data and compared against concurrent MODIS data from which chlorophyll was derived using two simple empirical algorithms. It was found that the MedOC3 algorithm outperforms the operational OC3M-547 algorithm and produces the least bias when compared against HPLC derived in situ chlorophyll. It is concluded that the greatest uncertainty in the inversion arises due to CDOM absorption below the 488 nm band. The reflectance ratios indicated that there is always an excess of yellow matter present in the study area and the water type could not be characterized optically as "typical open ocean" Case 1.},

note = {15-19 Μay },

keywords = {NE Aegean Sea, ocean colour, ocean optics, remote sensing},

pubstate = {published},

tppubtype = {conference}

}

@conference{Tsapanou2017,

title = {Estimating Suspended Particles Concentrations using Satellite and in-situ Ocean Colour Measurements in the Region of Fresh Water Influence of River Evros},

author = {A. Tsapanou and P.G. Drakopoulos and E. Oikonomou and S. Poulos},

url = {https://www.researchgate.net/publication/317358294_Estimating_Suspended_Particles_Concentrations_using_Satellite_and_in-situ_Ocean_Color_Measurements_in_the_Region_of_Fresh_Water_Influence_of_River_Evros_-_North_Aegean_Sea_Greece},

year  = {2017},

date = {2017-05-15},

address = {Lisbon Portugal},

organization = {3rd International Ocean Colour Science meeting},

abstract = {This study investigates the potential of remotely sensed data to map surface suspended particulate matter (SPM) in the Continental shelf area of the North-East Aegean in Greece, by using Landsat-8 satellite sensor. Initially, simultaneous above water ocean color measurements were validated against SPM field data and compared to a concurrent Landsat-8 image, obtained on low river discharge period (June 2016). The satellite imagery was atmospherically corrected and Landsat-8 Surface Reflectance data were generated from: the Landsat Surface Reflectance Code (LaSRC) provided by US Geological Survey and the FLAASH algorithm within the ENVI software. In both cases, the computed remote sensing reflectances (Rrs) from Landsat-8 are converted into SPM by adopting an algorithm based on single band analysis. After validation, the optical in-situ reflectances are correlated to Sentinel-2A corresponding spectral responses, thus leading to a single value for each band. A comparison between Landsat-8 estimations of SPM and concurrent optical measurements at 11 stations indicates that satellite-derived concentrations tend to overestimate sea-truth. Image processing through ENVI & USGS shows 83% correlation, whereas the best linear correlation (90%) is observed between optical and USGS-derived values. The Sentinel-2A optical responses are quite similar to those of Landsat-8. We further discuss the improvements required in coupled studies of SPM retrieval within the coastal zone, the relationship between the examined remote sensors, as well as the necessity to evaluate the Sentinel-2A imagery performance, not only at surface but within the water column using in-situ measurements.},

note = {15-19 Μay},

keywords = {Evros, ocean colour, river, satellite, water},

pubstate = {published},

tppubtype = {conference}

}

@conference{Chaikalis2016,

title = {Estimating zcat, in ultra-oligotrophic seas: implications for LISST-Deep scattering measurements,},

author = {S. Chaikalis and A.P. Karageorgis and S. Sofianos and P.G. Drakopoulos},

year  = {2016},

date = {2016-10-03},

pages = {1-6},

publisher = {University of Technology and Economics},

address = {Budapest Hungary},

organization = {5th Biennial Conference on Particles in Europe},

note = { October 3-5 },

keywords = {measurements, oligotrophic seas},

pubstate = {published},

tppubtype = {conference}

}

@conference{Ghionis2016,

title = {An integrated multispectral video and environmental monitoring system for the study of coastal processes and the support of beach management operations},

author = {G. Ghionis and V. Trygonis and A. Karydis and M. Vousdoukas and G. Alexandrakis and P.G. Drakopoulos and O. Amdreadis and F. Psarros and A. Velegrakis and S. Poulos  },

url = {https://www.researchgate.net/publication/303650866_An_integrated_multispectral_video_and_environmental_monitoring_system_for_the_study_of_coastal_processes_and_the_support_of_beach_management_operations},

year  = {2016},

date = {2016-01-02},

booktitle = {Geophysical Research Abstracts},

journal = {Geophysical Research Abstracts},

volume = {18},

number = {EGU2016-17240 },

organization = {EGU General Assembly 2016},

abstract = {Effective beach management requires environmental assessments that are based on sound science, are cost-effective and are available to beach users and managers in an accessible, timely and transparent manner. The most common problems are: 1) The available field data are scarce and of sub-optimal spatio-temporal resolution and coverage, 2) our understanding of local beach processes needs to be improved in order to accurately model/forecast beach dynamics under a changing climate, and 3) the information provided by coastal scientists/engineers in the form of data, models and scientific interpretation is often too complicated to be of direct use by coastal managers/decision makers. A multispectral video system has been developed consisting of one or more video cameras operating in the visible part of the spectrum, a passive near-infrared (NIR) camera, an active NIR camera system, a thermal infrared camera and a spherical video camera, coupled with innovative image processing algorithms and a telemetric system for the monitoring of coastal environmental parameters. The complete system has the capability to record, process and communicate (in quasi-real time) high frequency information on shoreline position, wave breaking zones, wave run-up, erosional hot spots along the shoreline, nearshore wave height, turbidity, underwater visibility, wind speed and direction, air and sea temperature, solar radiation, UV radiation, relative humidity, barometric pressure and rainfall. An innovative, remotely-controlled interactive visual monitoring system, based on the spherical video camera (with 360°field of view), combines the video streams from all cameras and can be used by beach managers to monitor (in real time) beach user numbers, flow activities and safety at beaches of high touristic value. The high resolution near infrared cameras permit 24-hour monitoring of beach processes, while the thermal camera provides information on beach sediment temperature and moisture, can detect upwelling in the nearshore zone, and enhances the safety of beach users. All data can be presented in real- or quasi-real time and are store for future analysis and training/validation of coastal processes models.},

note = {EGU General Assembly Vienna Austria },

keywords = {beach, coastal, monitor, multispectral, systems},

pubstate = {published},

tppubtype = {conference}

}

@conference{Drakopoulos2015d,

title = {Predicting Underwater Visibility in Tourist Beaches},

author = {P.G. Drakopoulos and Th. Gialelis and E. Pateras and S. Poulos and E. Stefanou},

editor = {E. Ozhan},

url = {https://beachtour.geol.uoa.gr/wp-content/uploads/2016/06/Drakopoulos-et-al.-2015.pdf},

year  = {2015},

date = {2015-12-10},

urldate = {2015-12-10},

pages = {977-984},

organization = {Proceedings of the Twelfth International Conference on the Mediterranean Coastal Environment MEDCOAST},

abstract = {Aiming towards supporting recreational snorkelling in tourist beaches, we have investigated the relationship between underwater visibility range and backscattering coefficient. A series of field experiments involving simultaneous monitoring of beam transmission, backscattering and underwater horizontal black disk sighting have been conducted in various locations. The first results indicate that monitoring backscattering, even in the red part of the spectrum, can provide a useful proxy for visibility determination with an estimated accuracy of20%.},

keywords = {beaches, colour, ocean colour, underwater},

pubstate = {published},

tppubtype = {conference}

}

@conference{Karageorgis2015b,

title = {Back to basics: Measuring IOPs in the Aegean Sea to support chlorophyll-α retrieval from ocean colour},

author = {A.P. Karageorgis and S. Psarra and P.G. Drakopoulos and G. Assimakopoulou and A.C. Banks and G. Kabouri and Th. Kanellopoulos and E. Krasakopoulou and A. Lagaria and K. Pagou and V. Papadopoulos and A. Papadopoulou and K. Parinos and P. Renieris and N. Spyridakis and D. Velaoras},

url = {https://www.researchgate.net/publication/293806678_Back_to_basics_Measuring_IOPs_in_the_Aegean_Sea_to_support_chlorophyll-a_retrieval_from_ocean_colour},

doi = {10.13140/RG.2.1.2181.8647},

year  = {2015},

date = {2015-12-07},

pages = {43-47},

address = {Brussels},

organization = {Final Scientific Conference of PERSEUS "Integrated Marine Research in the Mediterranean and the Black Sea"},

note = {7-9 December },

keywords = {chlorophyll a, ocean colour, optics},

pubstate = {published},

tppubtype = {conference}

}

@conference{A.2015,

title = { A novel approach for automated shoreline extraction from remote sensing images using low level programming},

author = {A. Rigos and A. Vaiopoulos and G. Skianis and G. Tsekouras and P.G. Drakopoulos },

url = {https://meetingorganizer.copernicus.org/EGU2015/EGU2015-7404.pdf},

year  = {2015},

date = {2015-05-01},

booktitle = {Geophysical Research Abstracts},

volume = {17},

address = {Vienna Austria},

organization = {EGU General Assembly 2015},

keywords = {laboratory, optics, optometry},

pubstate = {published},

tppubtype = {conference}

}

@conference{Drakopoulos2015b,

title = {Use of satellite images for monitoring the rate of retrieval of the coastline},

author = {P.G. Drakopoulos and E. Economou and G. Skianis and S. Poulos and Α. Vaiopoulos and Κ. Lazogiannis and G. Ghionis and Α. Velegrakis},

isbn = {978-960-9798-08-2},

year  = {2015},

date = {2015-05-01},

pages = {897-900},

organization = {Proc. 11th Panhel. Symp. Oceanogr. & Fish.},

keywords = {coastline, images, monitor, satellite},

pubstate = {published},

tppubtype = {conference}

}

@conference{Papadopoulou2015b,

title = {Estimation of temperature, salinity and scattering corrections of inherent optical properties using the AC-S in-situ spectrophotometer},

author = {A. Papadopoulou and P.G. Drakopoulos and A.P. Karageorgis and N. Spyridakis and S. Psarra and A.C. Banks and V. Zervakis},

url = {https://www.researchgate.net/publication/306441650_Estimation_of_temperature_salinity_and_scattering_corrections_of_inherent_optical_properties_using_the_AC-S_in-situ_spectrophotometer},

isbn = {978-960-9798-08-2},

year  = {2015},

date = {2015-05-01},

pages = {829-832},

organization = {Proc. 11th Panhel. Symp. Oceanogr. & Fish.},

abstract = {Absorption and attenuation data were collected in the North Aegean Sea during the Perseus and AegeanMarTech cruises using the spectral absorption and attenuation meter AC-S (WETLabs, Inc). Instrument drift, temperature, salinity and scattering corrections were applied to obtain accurate results. Negative absorption and attenuation coefficient values were observed at longer wavelengths. A range of methods were used to estimate absorption: the proportional scattering method appears to overestimate, while the flat method to underestimate absorption. The Kirk scattering method was found to provide the most reasonable results. However, further pure water calibrations are necessary to obtain more precise data.},

keywords = {absorption, AC-S scattering corrections methods, attenuation, ocean optics},

pubstate = {published},

tppubtype = {conference}

}

@conference{Psarra2015,

title = {Assessing phytoplankton dynamics in the Aegean Sea: combining remote sensing and field data of Chlorophyll a},

author = {S. Psarra and A. Lagaria and K. Pagou and G. Assimakopoulou and P.G. Drakopoulos and G. Petihakis and C. Frangoulis and G. Kakagiannis and M. Potiris and A. Banks and A. Karageorgis },

url = {https://www.researchgate.net/publication/306441730_Assessing_phytoplankton_dynamics_in_the_Aegean_Sea_combining_remote_sensing_and_field_data_of_Chlorophyll_a},

isbn = {978-960-9798-08-2},

year  = {2015},

date = {2015-05-01},

pages = {785-788},

organization = {Proc. 11th Panhel. Symp. Oceanogr. & Fish.},

abstract = {A compilation of 15 years field data of chlorophyll-a from the Aegean Sea are compared for the first time with respective remote sensing chlorophyll a matchups, using the MODIS-Aqua products and the OC3M-547 MODIS operational algorithm, along the trophic N-S gradients of the Aegean Sea. This is a small part of a coordinated study of the optical properties of the Aegean marine waters, undertaken for the first time within the framework of THALES-AegeanMarTech and PERSEUS-IP projects.},

keywords = {Aegean Sea, chlorophyll a, phytoplankton, remote sensing},

pubstate = {published},

tppubtype = {conference}

}

@conference{Drakopoulos2015,

title = {Above and in-water remote sensing reflectance measurements during the AegeanMarTech project: A first appraisal},

author = {P.G. Drakopoulos and A.C. Banks and G. Kakagiannis and A.P. Karageorgis and A. Lagaria and A. Papadopoulou and S. Psarra and N. Spyridakis and V. Zervakis},

url = {https://www.researchgate.net/publication/306441341_Above_and_in-water_remote_sensing_reflectance_measurements_during_the_AegeanMarTech_project_A_first_appraisal},

isbn = {978-960-9798-08-2},

year  = {2015},

date = {2015-05-01},

pages = {781-784},

organization = {Proc. 11th Panhel. Symp. Oceanogr. & Fish.},

abstract = {The optically complex properties of NE Aegean Sea were studied during the AegeanMarTech project. Simultaneous above and in-water ocean colour measurements were validated with chlorophyll concentration field data and compared against concurrent MODIS images. It was found that the Med-OC3 algorithm outperforms the operational OC3M-547 algorithm and produces the least bias when compared against HPLC derived in situ [Chl]. Satellite derived concentrations tend to underestimate [Chl] by >10% at best, the greatest uncertainty arising due to CDOM absorption below the 488 nm band. Relevant reflectance ratios indicated that there is always an excess of yellow mater present in the study area and the water type could not be characterized optically as " typical open ocean " Case 1. Further investigation is under way.},

keywords = {NE Aegean Sea, ocean color, ocean optics, remote sensing},

pubstate = {published},

tppubtype = {conference}

}

@conference{Karageorgis2015,

title = {Particle distribution and composition in the NE Aegean Sea based on transmissometry, optical backscattering and size measurements},

author = {A.P. Karageorgis and A. Androni and G. Assimakopoulou and A.C. Banks and P. Drakopoulos and G. Kabouri and Th. Kanellopoulos and E. Krasakopoulou and A. Lagaria and M. Morfis and K. Pagou and V. Papadopoulos and K. Parinos and S. Psarra and P. Renieris and N. Spyridakis},

url = {https://www.researchgate.net/publication/306441194_Particle_distribution_and_composition_in_the_NE_Aegean_Sea_based_on_transmissometry_optical_backscattering_and_size_measurements},

isbn = {978-960-9798-08-2},

year  = {2015},

date = {2015-05-01},

pages = {777-780},

organization = {Proc. 11th Panhel. Symp. Oceanogr. & Fish},

abstract = {The complex optical properties of NE Aegean Sea particles were studied in the framework of Perseus and AegeanMarTech projects. Inherent optical properties (IOPs; beam attenuation, optical backscattering, fluorescence) and discrete bottle data (PMC, POC, TChl-a) were measured during October 2013. Black Sea water (BSW) enters into the Aegean Sea from the Dardanelles and disperses to the west-northwest, as traced by characteristic salinity minima. The core of the BSW to the east of Limnos Island was relatively particle-enriched, showing maxima in beam c p , b bp , fluorescence, D 50 , PMC, POC, and TChl-a. Organic particles dominated in the upper water column, whereas resuspension of surface sediments was detected.},

keywords = {IOP, NE Aegean Sea, particle size, particulate matter, scattering},

pubstate = {published},

tppubtype = {conference}

}

@conference{Skianis2015,

title = {Spatial analysis of the behavior of the vegetation index NDVI over river Pinios Delta (Thessaly), using WorldView 2 Satellite imagery},

author = {G. Skianis and Α. Vaiopoulos and P. Drakopoulos and S.P. Poulos},

year  = {2015},

date = {2015-05-01},

pages = {1659-1670},

organization = {10th International congress of the Hellenic Geographical Society},

keywords = {analysis, imagery, rover, spatial, vegetation},

pubstate = {published},

tppubtype = {conference}

}

@conference{Papadopoulou2015,

title = {Deriving euphotic zone depth in the North Aegean Sea from field and MODIS ocean colour measurements},

author = {A. Papadopoulou and P. Drakopoulos and S. Psarra and A. Clive Banks and A. Karageorgis and A. Lagaria and N. Spyridakis and V. Zervakis , },

url = {https://www.researchgate.net/publication/306449205_Deriving_euphotic_zone_depth_in_the_North_Aegean_Sea_from_field_and_MODIS_ocean_colour_measurements},

year  = {2015},

date = {2015-05-01},

address = {Mykonos Island, Greece },

organization = {Fifth International CEMEPE and SECOTOX Conference},

abstract = {Euphotic zone depth (Zeu) is defined as the depth at which the photosynthetically active radiation (PAR) value is 1% of the surface value. In this work, three approaches were used to estimate Zeu from field data (in the North Aegean Sea): (a) the Chl-approach, where surface chlorophyll-a values were determined via the high performance liquid chromatography (HPLC) and the fluorometric technique, (b) the PAR-approach, where photosynthetically active radiation was measured with a hyperspectral irradiance meter and (c) the Reflectance-approach, in which surface reflectance values were produced from the in situ downwelling spectral irradiance and upwelling spectral radiance field measurements. Using the Seawifs Data Analysis System (SeaDAS), MODIS daily Level-2 Zeu datasets were produced with two different bio-optical algorithms, which were based on chlorophyll-a concentration (satellite Chl-approach). The comparison of field and satellite Zeu values showed that MODIS tended to underestimate the Zeu for all different approaches. In more detail, the two bio-optical algorithms were found to underestimate Zeu values by ~20-31% and ~18-21% when compared to field measured Zeu data via Chl-approach and PAR-approach, respectively. The percentage range of the underestimation of the Zeu satellite values compared with the one obtained from the field Zeu values via the Reflectance-approach, was found particularly small (~1-5%), a fact that explains the differences in the products as delivered by space agencies. Furthermore, the high uncertainties between field and satellite Zeu measurements require new approaches for ocean colour algorithms in the North Aegean Sea.},

keywords = {chlorophyll, euphotic zone, MODIS, ocean colour, remote sensing},

pubstate = {published},

tppubtype = {conference}

}