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.
