DISTORTION ON THE INTERRUPTED MODIFIED COLLIGNON PROJECTION
Keith C. Clarke
Department of Geology and Geography
Hunter College-CUNY
695 Park Ave.
New York, NY 10021, USA
and
Karen A. Mulcahy
Earth and Environmental Science Program
Graduate School and University Center-CUNY
33 West 42nd St.
New York, NY 10036, USA
ABSTRACT
The Interrupted Modified Collignon or "Clarke's Butterfly" projection is a
near-equal area pro- jection of the earth as a sphere onto eight
equilateral triangles, arranged as octants. This projection was presented
to solve a problem of mapping into an initial set of equilateral triangles
that could then be divided recursively into triangular quadtrees based on
Dutton's Quaternary Triangular Mesh. This projection was used as a test
case for experiments in designing a method for the visu- alization of map
projection distortion. We present a new method for portraying the
distortion, in which the projection parameters of local shape, area, and
direction are shown as several experi- mental combinations of red, green
and blue color intensity representations. Some of these combi- nations
show distinct promise as visualization methods for map distortion
portrayal, and assist greatly in the understanding of the Interrupted
Modified Collignon projection's spatial properties. Extension of the
method by its incorporation into map projection software is discussed, so
that map users will have a simple and effective means to visualize both
global maps, and their inherent inaccuracies.
Paper was presented at the GIS/LIS conference, 16th November, 1995 in
Nashville, TN.