Paper on 3D visualization in EMODnet Bathymetry published in Remote Sensing open access journal

30 January 2020

Since September 2018, the Bathymetry Viewing and Download service has been equipped with a powerful 3D visualization functionality that can be used in the browser without requirement of plugins. The 3D application is based on Cesium. However, a dedicated data structure has been developed by partners in EMODnet Bathymetry, in particular CORONIS, based on a triangulated irregular network (TIN). Having a TIN instead of a regular grid enables faster representation of the complexity of the map (i.e. the number and size of triangles). Software has been developed to create tiles in quantized mesh format out of a raster format such as used in the EMODnet DTM. Earlier, already a report a document while the software source can be found at GitHub.

Recently, also a scientific paper 3D Simplification Methods and Large Scale Terrain Tiling has been published in the Remote Sensing open access journal. This publication (ISSN 2072-4292) is a peer-reviewed open access journal about the science and application of remote sensing technology, and is published semi-monthly online by MDPI. The EMODnet Bathymetry paper tackles the problem of generating world-scale multi-resolution triangulated irregular networks optimized for web-based visualization. Starting with a large-scale high-resolution regularly gridded terrain, we create a pyramid of triangulated irregular networks representing distinct levels of detail, where each level of detail is composed of small tiles of a fixed size. The main contribution of this paper is to redefine three different state-of-the-art 3D simplification methods to efficiently work at the tile level, thus rendering the process highly parallelizable. These modifications focus on the restriction of maintaining the vertices on the border edges of a tile that is coincident with its neighbors, at the same level of detail. We define these restrictions on the three different types of simplification algorithms (greedy insertion, edge-collapse simplification, and point set simplification); each of which imposes different assumptions on the input data. We implement at least one representative method of each type and compare both qualitatively and quantitatively on a large-scale dataset covering the European area at a resolution of 1/16 of an arc minute in the context of the European Marine Observations Data network (EMODnet) Bathymetry project. The results show that, although the simplification method designed for elevation data attains the best results in terms of mean error with respect to the original terrain, the other, more generic state-of-the-art 3D simplification techniques create a comparable error while providing different complexities for the triangle meshes.