A global geographic grid system for visualizing bathymetry

Colin Ware1, Larry Mayer1, Paul Johnson1, Martin Jakobsson2, and Vicki Ferrini1

1Center for Coastal and Ocean Mapping, University of New Hampshire, Durham, NH 03924, USA
2Department of Geological Sciences, Stockholm University, Stockholm, Sweden
1Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA

Doi: 10.5194/gi-9-375-2020

Abstract
A global geographic grid system (Global GGS) is here introduced to support the display of gridded bathymetric data at whatever resolution is available in a visually seamless manner. The Global GGS combines a quadtree metagrid hierarchy with a system of compatible data grids. Metagrid nodes define the boundaries of data grids. Data grids are regular grids of depth values, coarse grids are used to represent sparse data and finer grids are used to represent high-resolution data. Both metagrids and data grids are defined in geographic coordinates to allow broad compatibility with the widest range of geospatial software packages. An important goal of the Global GGS is to support the meshing of adjacent tiles with different resolutions so as to create a seamless surface. This is accomplished by ensuring that abutting data grids either match exactly with respect to their grid-cell size or only differ by powers of 2. The oversampling of geographic data grids, which occurs towards the poles due to the convergence of meridians, is addressed by reducing the number of columns (longitude sampling) by powers of 2 at appropriate lines of latitude. In addition to the specification of the Global GGS, this paper describes a proof-of-concept implementation and some possible variants.