Floating Ring: A New Tool for Visualizing Distortion in Map Projections

We present a new method for interactive visualization of distortion in map projections. The central idea is a floating ring on the spheroid (globe) that can be interactively positioned and scaled. As the ring is manipulated on the globe, the corresponding projection of the ring is distorted using the same map projection parameters. We apply this method to study areal and angular distortion. This method is particularly useful when analyzing large geographical extents (such as in global climate studies) where distortions are significant, as well as visualizations for which information is geo-referenced and perhaps scaled to the underlying map. It serves as a reminder that distortions exist in maps and provides information about the degree, location, and type of distortion.