A software “tool kit” in C for the application of spherical geodesic grids in paleoclimatology

A popular technique in paleoclimatology is the definition of occurrences of climate-sensitive lithofacies, such as evaporite deposits, using a global grid system. The simplest and most widely used grid systems in paleoclimatology are orthogonal grids that use lines of latitude and longitude as grid-cell boundaries. Occurrences defined using orthogonal grids, however, can differ greatly in size and shape because lines of longitude converge at the poles, distorting the shape of the grid system. As a result of this distortion, the latitude at which the occurrences were defined can affect the number and distribution of occurrences. As an alternative, spherical geodesic systems can be used. Spherical geodesic systems have near-equal area and near-equal shape grid-cells for the entire sphere, which significantly reduce biases introduced by the grid system. Spherical geodesic systems can make paleoclimatic studies using occurrences of climate-sensitive lithofacies more reliable. To make spherical geodesic systems practical for paleoclimate applications, a “tool kit” of programs written in C has been assembled. Four programs are included in the tool kit: DESIGNER, which designs spherical geodesic grids, PLOTTER, which generates import files for Terra Mobilis™ and PGIS/Mac™ to display the grids, MAPPER, which defines occurrences using the grids, and ROTATOR, which rotates data about Euler poles. Middle Devonian evaporite data for North America were compiled to demonstrate each of the functions.