Keith C. Clarke
Department of Geology and Geography
695 Park Ave.
New York, NY 10021, USA
The study of global change requires an understanding of the distribution of atmospheric, natural, and human activities on the earth. Although the shape of the earth closely resembles an oblate ellipsoid, many data sets used for global change research are represented and analyzed in the form of flat maps or arrays. As we unbend the spherical surface of the earth and portray it as flat arrays of values it is inevitable that geometric distortion will occur. Since we are dealing with an inverse relationship between map scale and map projection distortion, small scale data sets such as those used in global change studies, have a greater amount of distortion. An appropriate choice of map projection is essential to minimize error. The visualization of map projection distortion assists researchers in choosing the best map projection.The choice of a projection for global change research should be based upon the type of analysis to be performed, the geographic area of interest, and the geometry of the map projection transformations. This research examines the various means for displaying map projection distortion available to global change researchers, with a special emphasis on the use of Tissot's Indicatrix and newly developed methods of distortion display for raster data sets. Increased understanding of map projection distortion through the use of visualization methods can considerably improve the accuracy of mapping global phenomena.
Paper was presented at the GIS/LIS conference, 16th November, 1995 in Nashville, TN.