Martian Crater Coordinates now in MDIM 2.1

In October 2010, the coordinates of the named craters in the Martian portion of the nomenclature database were updated from values from the Mars Digital Image Mosaic (MDIM) 2.0 control network to values in the MDIM 2.1 control network (see http://www.isprs.org/proceedings/XXXV/comm4/papers/464.pdf). The purpose of this work is to facilitate the identification of named Martian craters. The locations of the craters in the KML and shapefiles (http://planetarynames.wr.usgs.gov/GIS_Downloads) will correspond to the crater locations on any map product that was created using the same MDIM 2.1 control network.

The extents and sizes of the named craters were also updated; these data are approximate and are intended solely to give the user sufficient information to identify the craters and their rough extents. A link to a more precise global crater database by Stuart Robbins (see http://www.lpi.usra.edu/meetings/lpsc2010/pdf/2257.pdf) will be provided when available.

This new set of coordinates was derived using ArcMap version 9.3.1 and the Mars Digial Image Mosaic 2.1 (http://astrogeology.usgs.gov/Projects/MDIM21/). Some small craters are not resolved well in the MDIM 2.1 image; for these cases, feature coordinates were derived from the Thermal Emission Imaging System (THEMIS) Day IR 100m global mosaic (http://themis.asu.edu/news/themis-camera-yields-best-mars-map-ever). We would like to thank Stuart Robbins (University of Colorado, Boulder) for sharing a portion of his forthcoming global crater database, which provided a valuable and time-saving starting point for this work.

The Martian portion of the Gazetteer of Planetary Nomenclature now defaults to a new set of coordinates; the craters match MDIM 2.1, and the non-crater features are still in the MDIM 2.0 control network. The craters were updated first because they are the smallest features and therefore the mismatch between MDIM 2.0 and MDIM 2.1 was most obvious. Named non-crater features will be updated at a later date. The data set that contains all of the features in the MDIM 2.0 control network is still retained in the gazetteer, but is now considered archival and will not be updated with new names or changes to approved names.