Reliability of the Digital Sea Bottom Model Sourced by Multibeam Echosounder in Shallow Water

Abstract

Abstract Reliability of Digital Terrain Model created with geospatial data is a parameter in evaluation of its quality that takes into consideration both the method as well as the quality of data. Bathymetric surveys – dynamic measurements of a moving transducer of a singlebeam or multibeam echosounder used for depth measurements in water are a string of interrelated phenomena that determine the quality (accuracy) of geospatial coordinates. Inclusion of all factors influencing the accuracy of measurements, such as echosounder’s calibration, is a prerequisite for minimisation of systematic measurement errors. Random and gross errors are inevitable, and are eliminated during the cleaning process of geospatial data. High reliability, preliminarily filtered cloud of data is the initial source of the data for the creation of the Digital Sea Bottom Model. Comparison of two models using interpolation methods on the basis of discrete data carries the risk of the outcome being blurry. Cell size optimization on the basis of echosounder beams geometry is one of the essential parameters in quality assessment – two surface models comparison. Dynamic calibration of multibeam echosounder, based on the comparison of depths of outer edges of the bathymetric swath, is carried out utilizing raw data. Correct spatial orientation of echosounder’s head(s), due to the angular regulation of the echosounder’s head, minimizes discrepancies and increases the reliability of the data that is to be used to create the Digital Sea Bottom Model. This article presents the results of the analysis of accuracy of DSBM created with geospatial data acquired by multibeam echosounder, based on the calibration soundings that are the enabling stage for hydrographic surveys using MBES. The data used was recorded by R2Sonic multibeam echosounder in shallow waters (up to 30m depth), deriving from general rules of depths carting on nautical charts.