Map projections of irregular extraterrestrial objects

Abstract

Spatial information may relate not only to the Earth's surface, but also to other celestial bodies. Space probes send back to Earth more and more data, which are then processed and on their basis different kinds of cartographic products are created, such as hypsometric, topographic and albedo maps, virtual globes, spatial databases, terrain models etc.
In the case of solar system planets such as Venus, Mars, and the larger moons of the outer planets, typical map contains most often information about the terrain and the mutual spatial relations and the shape of characteristic forms of terrain (e.g, craters, plains, mountain ranges). The ellipsoid of rotation is usually taken as reference surface for these celestial bodies, because they are so massive that their own gravity forces get them close to a spherical shape.
However, in the solar system there is a significant number of so-called small celestial bodies with a diameter of up to several hundred kilometers (mainly asteroids and comets) whose shape is irregular. The impulse for the development of this kind of mapping is to obtain more accurate data source related to their surface. Particular attention should be paid to the satellites of Mars: Phobos and Deimos. The mapping of these objects requires the use of unconventional solutions in the selection of the reference surface and map projections.
The authors presented the basic problems of modern planetary cartography. They broadly described the problem of the use of map projections of irregular objects. They present basic types of map projections, their characteristics, as well as sample maps.