Real-time Monitoring of Uncertainty due to Refraction in Multibeam Echo Sounding

A software toolkit has been developed to objectively monitor uncertainty due to refraction in multibeam echosounding, specifically mapping systems that employ underway sound speed profiling hardware. The toolkit relies on the use of a raytrace simulator which mimics the sounding geometry of any given echosounder, specifically array type, angular sector, draft, and availability of a surface sound speed probe. The simulator works by objectively comparing a pair of consecutively collected sound speed profiles and reporting sounding uncertainty across the entire potential sounding space. Realtime visualizations of the uncertainty as a function of time and space allow the operator to tune the sound speed profile collection regime to maintain a desired sounding uncertainty while at the same time minimizing the number of casts collected

Reducing Black Carbon from Wood Burning in Fairbanks, Alaska

Fairbanks, Alaska has been home to air quality concerns for years. Heat sources like wood boilers emit black carbon, a pollutant akin to soot. In Fairbanks\u27s harsh winters, black carbon is trapped close to the earth and creates health problems for residents. Black carbon has a more global effect as well, however, and climate scientists have recently begun to consider reducing black carbon emissions as a viable way to slow the pace of climate change. Fairbanks is uniquely situated to react to this call for action. Reducing black carbon emissions from wood burning in Fairbanks would not only contribute to the greater fight against climate change, but would alleviate significant local air quality and health concerns. This Comment summarizes the issue of black carbon in Fairbanks, and proposes several legal approaches to mitigate its negative environmental and health effects, including public nuisance claims, local regulations, and stricter compliance with federal environmental laws

Note From the Editor

Denna rapport är en examensarbetsavhandling utförd vid KTH, Kungliga Tekniska Högskolan, under mars-augusti 2013. Arbetet har gjorts i samarbete med Nexus Marine som är en ledande tillverkare av marin navigationsutrustning för segelbåtar. Syftet med examensarbetet var att utveckla en ny konstruktionslösning för en vattentät kapsling till företagets instrument. Kapslingen skulle gå att öppna och stänga och skruv eller lim skulle inte användas i konstruktionen. Arbetet innefattade inte kapslingens yttre design som skall utföras i ett senare skede. Kapslingen skulle uppfylla de krav som finns uppställda för klassningen IPX7. Nexus Marines navigationssystem och nuvarande sortiment studerades för att ge en bild av vilka funktioner som kapslingen skulle innefatta och i vilken miljö den skulle användas. Befintliga vattentäta produkter på marknaden studerades även för att hitta olika lösningar för vattentäta konstruktioner. Studiebesök genomfördes på Plastsystem AB i Anderstorp, en av Nexus Marines tillverkare av plastdetaljer. Information om plastformsprutning, verktygsutformning och plastval samlades in. Telefonintervjuer hölls även senare under konstruktionsarbetet för frågor angående materialval etc. Standarden SS-EN 60529 studerades för att se vilka krav som skulle uppfyllas för klassningen IPX7 samt hur tester för att undersöka om de aktuella kraven är uppfyllda skulle gå tillväga. Ett antal koncept togs fram och visualiserades med 3D-modeller. Koncepten utvärderades med hjälp av en Pugh-matris. Det slutgiltiga konceptvalet diskuterades vid en workshop med anställda på företaget. Den slutgiltiga konstruktionen sammanfogas med snäppen längs instrumentets sidor. En front i transparent plast snäpps ihop med ett bakstycke. En yttre front snäpps sedan på för att dölja resterande delar av instrumentet. Mellan bakstycket och fronten placeras en skumgummitätning för att ge en vattentät sammanfogning. En prototyp togs fram i samarbetet med företaget Prototal AB för att utföra funktionstester av konstruktionen. Tester utfördes under vatten samt med tryckluft för ett antal olika tätningsmaterial. Slutligen togs förslag fram för hur konstruktionen skulle kunna förbättras utifrån resultatet av de prototyptester som genomförts.This report is a Master’s Degree Thesis written at KTH, Royal Institute of Technology, during March to August 2013. The project was done in collaboration with Nexus Marine, a leading developer of marine navigation systems for sailboats. The aim of this project was to develop a new design for a waterproof enclosure for the company’s equipment. The enclosure should be able to open and close and screws or glue should not be used in the design. The work did not include the outer design of the housing which should be done at a later stage. The enclosure should meet the requirement that is stated for IPX7. Nexus Marines navigation systems and current products were studied to give an idea of which features that should be included in the enclosure and in which environment it was supposed to be used. Existing waterproof products on the market was also studied to find different solutions for waterproof designs. A visit was made to Plastsystem AB in Anderstorp, one of Nexus Marines manufacturers of plastic details. Information about injection molding, design of manufacturing tools and plastic materials were collected. Telephone interviews were also held at a later stage in the design process regarding choice of materials etc. The standard SS-EN 60529 was studied to give information on which requirements that has to be met for IPX7 and how tests to see if these requirements are fulfilled should be conducted. A number of concepts were developed and visualized with 3D models. The concepts were evaluated using a Pugh matrix. The final concept selection was discussed at a workshop with employees at the company. The final design is joined with snap fits along the instruments sides. A front in a transparent plastic is snapped on to a back cover. An external front is then mounted to hide the rest of the instrument. A foam rubber gasket is placed between the back and front cover to give a waterproof joining of the parts. A prototype was developed in cooperation with Prototal AB to perform functional test of the design. Tests were done under water and with compressed air with a variety of different sealing materials. Proposals for how the design could be improved based on the results from the prototype tests were then presented

Modeling the Effect of Oceanic Internal Waves on the Accuracy of Multibeam Echosounders

When ray bending corrections are applied to multibeam echosounder (MBES) data, it is assumed that the varying layers of sound speed lie along horizontally stratified planes. In many areas internal waves occur at the interface where the water’s density changes abruptly (a pycnocline), this density gradient is often associated with a strong gradient in sound speed (a velocline). The internal wave introduces uncertainty into the echo soundings through two mechanisms: (1) tilting of the velocline, and (2) vertical oscillation of the velocline’s depth. A model has been constructed in order to examine how these effects degrade the accuracy of MBES measurements. The model numerically simulates the 3D ray paths of MBES soundings for a synthetic flat seafloor, as though the soundings have been collected through a user-defined internal wave. Along with sound speed information, the ray paths are used to estimate travel times which are then utilized as inputs for a conventional 2D ray trace. The discrepancy between the 3D and 2D ray traced solutions serve as an estimate of uncertainty. The same software can be extended to model the expected anomalies associated with tidal fronts and other phenomena that result in significant tilting or oscillation of the velocline. A case study was undertaken using observed internal wave parameters on the Scotian Shelf. The case study examines how survey design parameters such as line spacing, direction of survey lines, and water column sampling density can influence the uncertainty introduced by internal waves. In particular, an examination is undertaken in which 2D ray tracing models are augmented with MBES water column imaging of the velocline. The investigation shows that internal waves have the potential to cause vertical uncertainties exceeding IHO standards and that the uncertainty can potentially be mitigated through appropriate survey design. Results from the case study also indicate that acoustic tracking of the velocline has the potential to counteract the effects of internal waves through augmentation of 2D ray tracing models. This technique is promising, however, much more research and field testing is required to ascertain the practicality, reliability and repeatability of such an approach

Modelling Uncertainty Caused by Internal Waves on the Accuracy of MBES

A 3D ray tracing model has been developed to estimate the effects of internal waves upon the accuracy of multibeam echosounders (MBES). A case study examines the variability in these effects as a function of survey line direction and also considers the case of improving 2D ray tracing models with wave parameters derived from MBES water column imagery. Results indicate that, under certain circumstances, the effects of internal waves can prove to be a significant source of uncertainty that detracts from the ability to efficiently map the seafloor with wide swath angles