JSXGraph Geography: Maps and Globes as Constructions

Carsten Miller

Center for Mobile Learning with Digital Technology, University of Bayreuth, Germany

carsten.miller@uni-bayreuth.de

Abstract

Every flat world map distorts something. The property that is preserved – area, angle or distance – is a choice that is rarely made explicit to the reader. In September 2026, the UN General Assembly addressed this issue in Resolution A/RES/80/307. The resolution recommended equal-area projections, such as Equal Earth, for situations where relative size is important. It also requested that the limitations of flat maps be taught alongside these projections.

This talk presents JSXGraph Geography, an extension that adds two new features to JSXGraph: geomap, which draws the Earth on a plane using one of twelve interchangeable projections; and globe3d, which keeps the geometry on the sphere and inherits from view3d, enabling the globe to share its space with any other three-dimensional construction.

Sixteen drawable elements – including points, paths, markers, spherical triangles, regions, orbits and the day-and-night terminator – work on either host without knowing which one they are on. Everything remains a JSXGraph construction: points can be dragged, interactions fire events and measurements are taken on the sphere rather than on the screen. A path reports its length as it is drawn; therefore, a great circle and a rhumb line between the same two points will return different values. A spherical triangle reports its angle sum, the excess over 180 degrees and the resulting area.

As every interaction returns a value, the elements can be used in e-assessment as well as for illustration purposes. The data is included with the extension, so nothing is fetched from a tile server.