INTERPOLATION OVER LARGE DISTANCES USING SPHEREKIT

Spherekit is a spatial interpolation toolkit developed and distributed over the internet by the National Center for Geographic Information and Analysis (NCGIA). A unique feature of the software is its ability to work directly with the spherical geometry of the earth. Thus, distances, areas, and directions are spherically based, and interpolation can be carried out over large distances without distortions induced by the use of planar projections. The user can select from several interpolation methods that have been adapted to the sphere. The package also features "smart interpolation " capabilities to incorporate knowledge of the underlying physical processes that produced some of the spatial variability. Error analysis using cross-validation is built-in to compare the relative performance of interpolation algorithms or parameter settings. The cross-validation errors can themselves be interpolated to a uniform grid to reduce spatial bias. The capabilities of Spherekit are demonstrated using three examples