Tycho

The Tycho map was a collaborative effort between two brothers. The inspiration for this after-hours project was a joint interest in astronomy and a desire to experiment with the new cartographic tools in the ArcGIS suite. The map was honored with second prize at the poster session at the 2001 Northwest ESRI User Conference.

Crater Tycho is one of the most visually striking features on the moon's near side. The youngest large crater visible from Earth, Tycho is located south of Mare Nubium (Sea of Clouds) in the moon's heavily cratered southern highlands. Tycho has a diameter of 85 kilometers (53 miles). Average depth below rim is 4,700 meters (15,400 feet). A central peak rises 2,400 meters (7,800 feet) above the crater floor.

Tycho was formed about 100 million years ago when a large meteorite (or comet) collided with the moon. The resulting explosion vaporized vast amounts of the surrounding lunar surface, sending a large quantity of debris in a plume high above the moon. The intense heat generated by the impact melted rock, which splashed out of the crater forming an apron of melted material.

The data presented here portrays remotely sensed topography from Earth-based radio telescopes and orbital photographic images from the Clementine lunar spacecraft. Radar-derived digital elevation data was acquired in a PDS image format. The image was converted to an ArcInfo grid on a sinusoidal projection with a spherical radius of 1,748 kilometers. The elevation data has a vertical resolution of approximately 50 meters and a cell size (horizontal spacing) of 150 meters.

Topographic shading was achieved using a multidirectional hillshade algorithm weighted with an aspect image toward an illumination source at azimuth 293 degrees and an altitude of 50 degrees. Elevation ranges were then fused with the hillshade to create the relief map portrayed here. The orthographic scene was created using ArcInfo software's triangulated irregular network (TIN) surface modeling tools to drape a false-color Clementine orthophoto over a portion of the radar-derived elevation model. A vertical exaggeration factor of 2.5 was used to generate the wire-frame surface. The full 150-meter resolution was used to define the surface for draping, while 500-meter spacing was used for the mesh area.

The images show Tycho elevation data through nine stages of illumination. The frames simulate from right to left the illumination of the crater from waxing gibbous through full and waning gibbous phases. Topographic shading for the images was achieved using ArcInfo software's grid hillshade command.