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1 2006

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Analiza porównawcza metod modelowania powierzchni w aspekcie opracowania numerycznego modelu dna morskiego

Łubczonek J.

Roczniki Geomatyki

2006

T. 4, z. 3

151-163

One of the basic information used in marine navigation is bathymetric information, which allows determining safe navigation water area. Presently, it is not only used in ship handling but also in coastal systems of port management or dynamic prediction of under keel clearance systems for precise assessment the ship draught. The bathymetric information such as soundings, contour lines, depth areas, is the basic content of paper or electronic charts. In the case of the latter, we can observe a steady trend to implement three-dimensional presentation of seabed, either on the level of conception project or in commercial products (charts used in fishing and marine navigation). We should also remember about new products such as bathymetric charts, which will be a part of marine maps or charts used in inland shipping (InlandECDIS). Current development of technology has changed the way of collecting and processing bathymetric data. By using multibeam echo sounders hydrographs can collect high density data points. This had a strong influence on development of marine charts and related products. Application of modern remote sensing allows, on the one hand, for 100 % coverage of the sea bottom by sounding but, on the other hand, requires proper processing of data points for building a numerical model of sea bottom. This final phase is very important because it decides on the accuracy of bathymetric information. Elaboration of numerical models of seabed is complicated, first of all, by large data sets, which can consist of billions of data points or more. In many programs, which implement code for DTM elaboration we can find general recommendations, which not always make it possible to select proper modeling methods. Additionally, application the two techniques of data collecting . by using multi and singlebeam echo sounders poses certain problems. The first one is rather obligatory for most port areas, while the second is also used for controlling and updating seabed bathymetry. While elaborating DTM of seabed we can have low density data sets with regular spatial distribution (data registered by singlebeam echo sounders) or high density data sets with differential spatial distribution (data registered by multibeam echo sounders) This paper shows comparative analysis of surface modeling methods including many factors having influence on the final error of model approximation. Apart from including influence of surface shape, the study also focused on influence of measurement data density and structure, adequate for applied technique of bathymetric data collecting. During research simulated mathematical surfaces were used, which enable to asses and determine the error of surface approximation. Numerical terrain models were built by using triangulation, weighted average methods, kriging, methods based on radial basis functions and others, applied during geographical surface modeling. The analysis explains the complexity of the process of creating a seabed numerical model with regard to elaborating a model accurately representing the real surface. The results of the research can be useful during DTM of the sea bottom creation or in elaborating models from data points with similar density and structure.