Professor
Emeritus Email:
tobler@geog.ucsb.edu An
experimental spherical quadratic transportation model is applied to world
exports and imports. The data consists of a table of 1987 trade (in millions of
dollars) between seventy countries distributed thoughout the world. One version
of the model uses the 4900 spherical distances between the country centroids.
The model then generates supply and demand Lagrangians and attractivity and
turnover potentials from the table margins. A variant of this model includes
the summed exports and imports as weights. Both of these model estimates can be
compared to the actual trade table. An alternate form of the model solves the
spherical Poisson equation to get the attractivity potential. Gradient and
streakline fields are computed from this net movement potential, and are shown
in the form of maps.
Geography Department
University of California
Santa Barbara, CA 93106-4060