A Novel Approach of Using Selected Unconventional Geodesic Methods of Estimation on VTS Areas     

Krzysztof Czaplewski  Mariusz Wąż  Marek Hubert Zienkiewicz 《Marine Geodesy》2013,36(5):447-468

Abstract

The Vessel Traffic Service (VTS) systems belong to the fundamental tools used in ensuring a high level of safety across sea basins with heavy traffic, where the presence of navigational hazards poses a great risk of collision or a ship running aground. In order to determine the mutual location of ships, VTS systems obtain information from different facilities, such as coastal radar stations, AIS, and vision systems. Fixing a ship’s position is always accompanied by a degree of error, but the degree of error depends on the specific position fixing system used. In order to increase the accuracy of position fixing in VTS systems, the authors propose the use of contemporary geodetic methods. The article presents the theoretical fundamentals of two unconventional geodesic methods of estimation: M estimation and M_split(q)estimation and the authors’ own proposal of their application in VTS systems. The article concludes with a test verifying theoretical assumptions, performed with the use of a computer application allowing position fixing with the use of selected robust adjustment methods. Furthermore, an example is presented of M_split(q)estimation as used for the acquisition of low-signal radar echoes, which in VTS systems are not automatically identified for tracking. The level of the echo signal makes it difficult for a VTS controller to separate these objects from typical radar noise and interference.  相似文献   

Flow dynamics at the origin of thin clayey sand lacustrine turbidites: Examples from Lake Hazar,Turkey          下载免费PDF全文

Sophie Hage  Aurélia Hubert‐Ferrari  Laura Lamair  Ulaş Avşar  Meriam El Ouahabi  Maarten Van Daele  Frédéric Boulvain  Mohamed Ali Bahri  Alain Seret  Alain Plenevaux 《Sedimentology》2017,64(7):1929-1956

Turbidity currents and their deposits can be investigated using several methods, i.e. direct monitoring, physical and numerical modelling, sediment cores and outcrops. The present study focused on thin clayey sand turbidites found in Lake Hazar (Turkey) occurring in eleven clusters of closely spaced thin beds. Depositional processes and sources for three of those eleven clusters are studied at three coring sites. Bathymetrical data and seismic reflection profiles are used to understand the specific geomorphology of each site. X‐ray, thin sections and CT scan imagery combined with grain‐size, geochemical and mineralogical measurements on the cores allow characterization of the turbidites. Turbidites included in each cluster were produced by remobilization of surficial slope sediment, a process identified in very few studies worldwide. Three types of turbidites are distinguished and compared with deposits obtained in flume studies published in the literature. Type 1 is made of an ungraded clayey silt layer issued from a cohesive flow. Type 2 is composed of a partially graded clayey sand layer overlain by a mud cap, attributed to a transitional flow. Type 3 corresponds to a graded clayey sand layer overlain by a mud cap issued from a turbulence‐dominated flow. While the published experimental studies show that turbulence is damped by cohesion for low clay content, type 3 deposits of this study show evidence for a turbulence‐dominated mechanism despite their high clay content. This divergence may in part relate to input variables, such as water chemistry and clay mineralogy, that are not routinely considered in experimental studies. Furthermore, the large sedimentological variety observed in the turbidites from one coring site to another is related to the evolution of a sediment flow within a field‐scale basin made of a complex physiography that cannot be tackled by flume experiments.  相似文献   

Panta Rhei 2013–2015: global perspectives on hydrology,society and change     

Hilary McMillan  Alberto Montanari  Christophe Cudennec  Hubert Savenije  Heidi Kreibich  Tobias Krueger 《水文科学杂志》2013,58(7):1174-1191

ABSTRACT

In 2013, the International Association of Hydrological Sciences (IAHS) launched the hydrological decade 2013–2022 with the theme “Panta Rhei: Change in Hydrology and Society”. The decade recognizes the urgency of hydrological research to understand and predict the interactions of society and water, to support sustainable water resource use under changing climatic and environmental conditions. This paper reports on the first Panta Rhei biennium 2013–2015, providing a comprehensive resource that describes the scope and direction of Panta Rhei. We bring together the knowledge of all the Panta Rhei working groups, to summarize the most pressing research questions and how the hydrological community is progressing towards those goals. We draw out interconnections between different strands of research, and reflect on the need to take a global view on hydrology in the current era of human impacts and environmental change. Finally, we look back to the six driving science questions identified at the outset of Panta Rhei, to quantify progress towards those aims.