Mapping Mars: Geodetic and cartographic aspects

This paper presents a review of geodetic and cartographic aspects involved in the mapping of Mars and in the handling of planetary data returned and available from different team missions. It focuses on the reference system adopted for the planet, the main coordinate systems being used and main projection systems adopted when representing the data in a map. Several returned data are available in two different coordinate systems, the planetographic and the planetocentric. Errors in latitude and longitude when taking one system for another are addressed and quantified. As an example, the difference between planetographic and planetocentric latitudes can reach up to ~0.35°. Errors involving equirectangular, sinusoidal and stereographic map projections, which are among the most common projections used to represent Mars data, are studied. Angular, linear and areal distortions are calculated for all three projections and the results are discussed. For the given examples, the maximum angular distortion and the distortion along parallels for a typical HiRISE image were ~0.6° and ~1.009, respectively. For the MOC image used in the examples, the maximum angular distortion and the distortion along meridians were ~0.02° and ~1.00000005, respectively. And for the stereographic projection the distortion along meridians was ~1.049150.