Shallow Water Bathymetry Mapping from UAV Imagery based on Machine Learning

The determination of accurate bathymetric information is a key element for near offshore activities, hydrological studies such as coastal engineering applications, sedimentary processes, hydrographic surveying as well as archaeological mapping and biological research. UAV imagery processed with Structure from Motion (SfM) and Multi View Stereo (MVS) techniques can provide a low-cost alternative to established shallow seabed mapping techniques offering as well the important visual information. Nevertheless, water refraction poses significant challenges on depth determination. Till now, this problem has been addressed through customized image-based refraction correction algorithms or by modifying the collinearity equation. In this paper, in order to overcome the water refraction errors, we employ machine learning tools that are able to learn the systematic underestimation of the estimated depths. In the proposed approach, based on known depth observations from bathymetric LiDAR surveys, an SVR model was developed able to estimate more accurately the real depths of point clouds derived from SfM-MVS procedures. Experimental results over two test sites along with the performed quantitative validation indicated the high potential of the developed approach.Comment: 8 pages, 9 figure

SPATIAL DISTRIBUTION REQUIREMENTS OF REFERENCE GROUND CONTROL FOR ESTIMATING LIDAR/INS BORESIGHT MISALIGNMENT

LiDAR (Light Detection and Ranging, also known as Airborne Laser Scanning – ALS) is a powerful technology for obtaining detailed and accurate terrain models as well as precise description of natural and man-made objects from airborne platforms, with excellent vertical accuracy. High performance integrated GPS/INS systems provide the necessary navigation information for the LiDAR data acquisition platform, and therefore, the proper calibration of the entire Mobile Mapping System (MMS) including individual and inter-sensor calibration, is essential to determine the accurate spatial  relationship of the involved sensors. In particular, the spatial relationship between the INS body frame and the LiDAR body frame is of high importance as it could be the largest source of systematic errors in airborne MMS. The feasibility of using urban areas, especially buildings, for boresight misalignment is still investigated. In this research, regularly or randomly distributed, photogrammetrically restituted buildings are used as reference surfaces, to investigate the impact of  the spatial distribution and the distance between the necessary ‘building-positions’ on boresight’s misalignment parameter estimation. The data used for performance evaluation included LiDAR point clouds Pothou, A. et al  777 and aerial images captured in a test area in London, Ohio, USA. The city includes mainly residential houses and a few bigger buildings

Differential Regulation of Growth-Promoting Signalling Pathways by E-Cadherin

Background: Despite the well-documented association between loss of E-cadherin and carcinogenesis, as well as the link between restoration of its expression and suppression of proliferation in carcinoma cells, the ability of E-cadherin to modulate growth-promoting cell signalling in normal epithelial cells is less well understood and frequently contradictory. The potential for E-cadherin to co-ordinate different proliferation-associated signalling pathways has yet to be fully explored. Methodology/Principal Findings: Using a normal human urothelial (NHU) cell culture system and following a calcium-switch approach, we demonstrate that the stability of NHU cell-cell contacts differentially regulates the Epidermal Growth Factor Receptor (EGFR)/Extracellular Signal-Regulated Kinase (ERK) and Phosphatidylinositol 3-Kinase (PI3-K)/AKT pathways. We show that stable cell contacts down-modulate the EGFR/ERK pathway, whilst inducing PI3-K/AKT activity, which transiently enhances cell growth at low density. Functional inactivation of E-cadherin interferes with the capacity of NHU cells to form stable calcium-mediated contacts, attenuates E-cadherin-mediated PI3-K/AKT induction and enhances NHU cell proliferation by allowing de-repression of the EGFR/ERK pathway and constitutive activation of beta-catenin-TCF signalling. Conclusions/Significance: Our findings provide evidence that E-cadherin can differentially and concurrently regulate specific growth-related signalling pathways in a context-specific fashion, with direct, functional consequences for cell proliferation and population growth. Our observations not only reveal a novel, complex role for E-cadherin in normal epithelial cell homeostasis and tissue regeneration, but also provide the basis for a more complete understanding of the consequences of E-cadherin loss on malignant transformation

Forecasting Exchange-Rates via Local Approximation Methods and Neural Networks

There has been an increased number of papers in the literature in recent years, applying several methods and techniques for exchange - rate prediction. This paper focuses on the Greek drachma using daily observations of the drachma rates against four major currencies, namely the U.S. Dollar (USD), the Deutsche Mark (DM), the French Franc (FF) and the British Pound (GBP) for a period of 11 years, aiming at forecasting their short-term course by applying local approximation methods based on both chaotic analysis and neural networks.Key Words: Exchange Rates, Forecasting, Neural Networks

How schlieren affects beam transmissometers and LISST-Deep: an example from the stratified Danube River delta, NW Black Sea

The term ‘schlieren’ describes angular deflection of a light ray when it passes through a fluid region characterized by refractive index inhomogeneities. These inhomogeneities in the marine environment are generally caused by density variations, i.e. salinity and temperature anomalies. The influence of schlieren on transmissometers and the in situ particle sizer LISST-Deep of Sequoia Scientific are examined in the Danube delta during October 2007. A seasonal pycnocline driven mainly by an intense temperature gradient was identified as a major hydrological feature. It was associated with high buoyancy frequency values and minor changes of the refractive index of seawater. Measurements of two 25-cm path-length transmissometers (660 nm and 470 nm) showed distinguishable peaks at the pycnocline. LISST also uses a 5-cm transmissometer (670 nm), which proved to be very sensitive in both cases. This is mainly due to its very small acceptance angle, which enables enhanced light scattering outside the lens, thus increasing beam attenuation. Subsequently, LISST falsely predicts abundance of large particles within the pycnoclines. A buoyancy frequency N of 0.01 s-1 is the new proposed threshold for schlieren occurrence

3D EDGE DETECTION AND COMPARISON USING FOUR-CHANNEL IMAGES

Point cloud segmentation, is a widespread field of research and it is useful in several research topics and applications such as 3D point cloud analysis, scene understanding, semantic segmentation etc. Architectural vector drawings constitute a valuable platform source for scientists and craftsmen while the production of such drawings is time-consuming because many of the creation steps are done manually. Detecting 3D edges in point clouds could provide useful information for the automation of the creation of 3D architectural vector drawings. Hence, a 3D edge detection method is proposed and evaluated with a proof-of-concept experiment and another one using a professional software. The scope of this effort is twofold, firstly the production of semantically enriched 3D dense point clouds exploiting four-channel images in order to detect 3D edges and secondly the comparison of the detected 3D edges with their corresponding edges in a textured 3D model. Comparing 3D edges in the early step of the 3D dense point cloud production and in the final step of 3D textured mesh, provides useful conclusions of the data used for the automatic creation of 3D drawings. Both of the experiments i.e., the proof-of-concept and using the professional SfM-MVS software were conducted using real world data of cultural heritage objects

Ubiquinone-8 Stimulates Phagocytosis in Macrophages by Modulation of the Kinetics of the Fc Receptor

The effect of exogenous ubiquinone-8 (Q8) on IgG- and C3b-mediated phagocytosis of sensitized sheep red blood cells and of opsonized Staphylococcus aureus by macrophages was studied by morphological and quantitative methods. Q8 stimulated the initial events of phagocytosis, that is, attachment and ingestion, in which occupancy of the Fe receptor by IgG was shown to be of critical significance. The kinetics of competitive inhibition of phagocytosis of opsonized bacteria by macrophages by using Fe fragments suggested the intimate role of the kinetics of the Fe receptor in the initial events of phagocytosis and, further, the modulation of the kinetics of the Fe receptor by Q8 as the basis of enhanced phagocytosis by Q

REASSEMBLY OF ROCK SEGMENTS, THE CASE OF AREOPAGUS HILL

There are no specifications and/or standards for the restoration of collapsed masses of rocks, as in most cases the rocks bear no historical/archaeological value and their restoration would require significant budget and resources. But plenty of colossal statues, ancient temples, tombs and whole cities are carved on the surface or even expand in the interior of solid natural rocks. These so-called rock-cut monuments are located all around the globe and, in most cases, are made on a grand scale. Earthquakes, rock’s faults, erosion and karst can lead to massive rock collapses.The purpose of this paper is to establish an integrated methodology for the relocation of detached rock segments to their original positions. Specifically, the proposed methodology is based on the case of the Areopagus Hill and involves the generation of 3d models of the rock segments, their virtual reassembly and their utilization for the reconstruction of a part of the peak of the hill