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The process of modelling the elevation surface of a coastal area using the fusion of spatial data from different sensors

Włodarczyk-Sielicka Marta, Bodus-Olkowska Izabela, Łącka Małgorzata

Oceanologia

2022

No. 64 (1)

22--34

Information regarding the depth distribution in a specific aquatic area is not also crucial for the safety of navigation, but also for modelling environmental processes, such as the quick establishment of marine-land boundaries or assessments of flood risk areas. Using elevation data from different available sources can be very convenient for individuals who wish to conduct quick analysis or need to obtain data covering a large area without the need for data collection and surveys. This study proposes a method of combining spatial data from different sources during surface modelling of a coastal area. The spatial data used for elevation surface modelling included hydrographic and topographic data, which are often collected separately for various purposes. Data are saved in different formats with various resolutions and accuracies; thus, a uniform surface model that will allow for easy and accurate analysis is currently lacking. The main aim of this study was to create a model of the surface of a coastal area using input data from various sources with the highest possible accuracy. This paper presents the available spatial data sources for coastal areas, along with the data pre-processing process. Furthermore, spatial data fusion is introduced, along with the results. The entire process of creating the uniform surface model consisted of several steps that are described in detail and visualised. The obtained model was visualised using a three-dimensional map.

NOAA Marine Geophysical Data and a GEBCO Grid for the Topographical Analysis of Japanese Archipelago by Means of GRASS GIS and GDAL Library

Lemenkova Polina

Geomatics and Environmental Engineering

2020

Vol. 14, no. 4

25--45

This article analyzes topographical and geological settings in the Japan Archipelago for comparative raster data processing using GRASS GIS. Data include bathymetric and geological grids in NetCDF format: GEBCO, EMAG2, GlobSed, marine free-air gravity anomaly and EGM96. Data were imported to GRASS by gdalwarp utility of GDAL and projected via PROJ library. Methodology includes data processing (projecting and import), mapping and spatial analysis. Visualization was done by shell scripting using a sequence of GRASS modules: ‘d.shade’ for relief mapping, ‘r.slope.aspect’; for modelling based on DEM, ‘r.contour’ for plotting isolines, ‘r.mapcalc’ for classification, ‘r.category’ for associating labels, and auxiliary modules (d.vect, d.rast, d.grid, d.legend). The results of the geophysical visualization show that marine free-air gravitational anomalies vary in the Sea of Japan (–30 to above 40 mGal) reflecting density inhomogeneities of the tectonic structure, and correlating with the geological structure of the seafloor. Dominating values of geoid model are 30–45 m reflecting West Pacific rise, determined by deep density inhomogeneities associated with the mantle convention. Sediment thickness varies across the sea reflecting its geological development with density of 2 km in its deepest part and thinner in central part (Yamato Rise). The aspect map and reclassified map express gradient of the steepest descent.