Providing the Third Dimension: High-resolution Multibeam Sonar as a Tool for Archaeological Investigations - An Example from the D-day Beaches of Normandy

In general, marine archaeological investigations begin in the archives, using historic maps, coast surveys, and other materials, to define submerged areas suspected to contain potentially significant historical sites. Following this research phase, a typical archaeological survey uses sidescan sonar and marine magnetometers as initial search tools. Targets are then examined through direct observation by divers, video, or photographs. Magnetometers can demonstrate the presence, absence, and relative susceptibility of ferrous objects but provide little indication of the nature of the target. Sidescan sonar can present a clear image of the overall nature of a target and its surrounding environment, but the sidescan image is often distorted and contains little information about the true 3-D shape of the object. Optical techniques allow precise identification of objects but suffer from very limited range, even in the best of situations. Modern high-resolution multibeam sonar offers an opportunity to cover a relatively large area from a safe distance above the target, while resolving the true three-dimensional (3-D) shape of the object with centimeter-level resolution. A clear demonstration of the applicability of highresolution multibeam sonar to wreck and artifact investigations occurred this summer when the Naval Historical Center (NHC), the Center for Coastal and Ocean Mapping (CCOM) at the University of New Hampshire, and Reson Inc., collaborated to explore the state of preservation and impact on the surrounding environment of a series of wrecks located off the coast of Normandy, France, adjacent to the American landing sectors The survey augmented previously collected magnetometer and high-resolution sidescan sonar data using a Reson 8125 high-resolution focused multibeam sonar with 240, 0.5° (at nadir) beams distributed over a 120° swath. The team investigated 21 areas in water depths ranging from about three -to 30 meters (m); some areas contained individual targets such as landing craft, barges, a destroyer, troop carrier, etc., while others contained multiple smaller targets such as tanks and trucks. Of particular interest were the well-preserved caissons and blockships of the artificial Mulberry Harbor deployed off Omaha Beach. The near-field beam-forming capability of the Reson 8125 combined with 3-D visualization techniques provided an unprecedented level of detail including the ability to recognize individual components of the wrecks (ramps, gun turrets, hatches, etc.), the state of preservation of the wrecks, and the impact of the wrecks on the surrounding seafloor

Application of High-precision Timing Systems to Distributed Survey Systems

In any hydrographic survey system that consists of more than one computer, one of the most difficult integration problems is to ensure that all components maintain a coherent sense of time. Since virtually all modern survey systems are of this type, timekeeping and synchronized timestamping of data as it is created is of significant concern. This paper describes a method for resolving this problem based on the IEEE 1588 Precise Time Protocol (PTP) implemented by hardware devices, layered with some custom software called the Software Grandmaster (SWGM) algorithm. This combination of hardware and software maintains a coherent sense of time between multiple ethernet-connected computers, on the order of 100 ns (rms) in the best case, of the timebase established by the local GPS-receiver clock. We illustrate the performance of this techniques in a practical survey system using a Reson 7P sonar processor connected to a Reson 7125 Multibeam Echosounder (MBES), integrated with an Applanix POS/MV 320 V4 and a conventional data capture computer. Using the timing capabilities of the PTP hardware implementations, we show that the timepieces achieve mean (hardware based) synchronization and timestamping within 100-150 ns (rms), and that the data created at the Reson 7P without hardware timestamps has a latency variability of 28 µs (rms) due to software constraints within the capture system. This compares to 288 ms (rms) using Reson’s standard hybrid hardware/software solution, and 13.6 ms (rms) using a conventional single-oscillator timestamping model

High-Precision, High-Accuracy Timekeeping in Distributed Survey Systems

Accurate and precise timekeeping between computers in a distributed survey system is essential to ensure adequate data quality, especially with Multibeam Echosounders (MBES) which can otherwise suffer from significant motion artefacts. We show that clock synchronisation on the order of 100-150ns (rms) is readily achievable in a modern MBES-based survey system utilising an Ethernet-based time synchronisation mechanism and some custom timekeeping software. We also show that improving the timekeeping eliminates motion artefacts in the observed bathymetry, and simplifies the patch-test procedure.Para asegurar una calidad adecuada de los datos es esencial una exacta y precisa mantencion de la hora entre ordenadores en un sistema de levantamiento distribuido, especialmente con Sondadores Acusticos Multihaz (MBES), que sino pueden experimentar las consecuencias de un significativo movimiento de sus artefactos. Mostramos que la sincronizaci6n de un reloj en el orden de 100-150ns (rms) puede llevarse a cabo facilmente en un sistema moderno de levantamientos efectuados mediante MBES, utilizando un mecanismo Ethernet basado en la sincronizacion del tiempo y en algun programa de mantencion de la hora adaptado. Tambien mostramos que mejorando la mantencion de la hora se elimina el movimiento de los artefactos en la batimetria observada, y simplifica el procedimiento de pruebas en parches.Il est essentiel d'avoir un chronometrage exact et precis entre ordinateurs dans un systeme integre pour les leves hydrographiques afin d'assurer une qualite des donnees appropriee notamment pour les sondeurs multifaisceaux (MBES) qui, dans le cas contraire, peuvent patir de perturbations significatives liees au mouvement. Nous montrons qu'une synchronisation des horloges de l'ordre de 100 a 150ns (valeur quadratique moyenne) est facilement obtenue dans un systeme de leves moderne reposant sur les MBES et utilisant un mecanisme de synchronisation du temps dans un reseau Ethernet et un logiciel specifique de chronometrage. Nous demontrons egalement que l'amelioration du chronometrage permet de supprimer certaines perturbations liees au mouvement dans la bathymetrie observee et de simplifier la procedure d'essai par plage

preliminary trials to rear the copepod temora stylifera as food for fish larvae

AbstractCopepods represent an important natural food supply for many fish larvae but they are not commonly used in aquaculture. The aim of this project is: 1) to set up an experimental re-circulating system to breed the copepod Temora stylifera and 2) to replace Artemia salina with T. stylifera as live food for Sparus aurata larvae. The choice of this copepod species has been based on both its abundance in the Mediterranean as well as its characteristics in terms of size and nutritional value. The re-circulating system consists of a collecting water tank of 1,000 litre of capacity, a thermoregulation system, two 500 litre tanks to rear adults and two 200 litre tanks to collect nauplii. The system allows the computerised water re-circle and to concentrate and collect nauplii through their positive response to light. It can work both in a partial re-circle way, for the thermoregulation only, as well as in a total re-circle way for the water purification through mechanic and biological filters. The culture s..

High-Precision, High-Accuracy Timekeeping in Distributed Survey Systems

Accurate and precise timekeeping between computers in a distributed survey system is essential to ensure adequate data quality, especially with Multibeam Echosounders (MBES) which can otherwise suffer from significant motion artefacts. We show that clock synchronisation on the order of 100-150ns (rms) is readily achievable in a modern MBES-based survey system utilising an Ethernet-based time synchronisation mechanism and some custom timekeeping software. We also show that improving the timekeeping eliminates motion artefacts in the observed bathymetry, and simplifies the patch-test procedure.Para asegurar una calidad adecuada de los datos es esencial una exacta y precisa mantencion de la hora entre ordenadores en un sistema de levantamiento distribuido, especialmente con Sondadores Acusticos Multihaz (MBES), que sino pueden experimentar las consecuencias de un significativo movimiento de sus artefactos. Mostramos que la sincronizaci6n de un reloj en el orden de 100-150ns (rms) puede llevarse a cabo facilmente en un sistema moderno de levantamientos efectuados mediante MBES, utilizando un mecanismo Ethernet basado en la sincronizacion del tiempo y en algun programa de mantencion de la hora adaptado. Tambien mostramos que mejorando la mantencion de la hora se elimina el movimiento de los artefactos en la batimetria observada, y simplifica el procedimiento de pruebas en parches.Il est essentiel d'avoir un chronometrage exact et precis entre ordinateurs dans un systeme integre pour les leves hydrographiques afin d'assurer une qualite des donnees appropriee notamment pour les sondeurs multifaisceaux (MBES) qui, dans le cas contraire, peuvent patir de perturbations significatives liees au mouvement. Nous montrons qu'une synchronisation des horloges de l'ordre de 100 a 150ns (valeur quadratique moyenne) est facilement obtenue dans un systeme de leves moderne reposant sur les MBES et utilisant un mecanisme de synchronisation du temps dans un reseau Ethernet et un logiciel specifique de chronometrage. Nous demontrons egalement que l'amelioration du chronometrage permet de supprimer certaines perturbations liees au mouvement dans la bathymetrie observee et de simplifier la procedure d'essai par plage

Open bite: classification and etiopathogenetic examination

In the present study different types of "open-bite" have been taken under consideration. First of all, have been analysed the main etiopathogenetic factors which are the causes of the malformation in sphere of various classifications