In late 2010, the coordinates of the named features in the Mercury portion of the nomenclature database were updated from values from historical sources to values in the preliminary MESSENGER control network. The purpose of this work was to facilitate the identification of named features on Mercury. Dots representing the coordinates of the centers of named features will fall in the centers of the features when displayed on any map product that was created using the same control network.
The extents and sizes of the named features were also updated; these data are approximate and are intended solely to give the user sufficient information to identify named features and their rough extents.
This new set of coordinates was derived using ArcMap version 9.3.1 and the global map of Mercury. Because MESSENGER does not yet have global coverage of Mercury, Mariner 10 data were used to fill in areas where MESSENGER has not yet collected image data. In order for the two data sets to align, the preliminary MESSENGER control network was tied to the Mariner 10 map using several ground truth points.
The Mercury portion of the Gazetteer of Planetary Nomenclature web site now defaults to showing feature coordinates in the frame of the preliminary MESSENGER control network. The original ‘unknown’ source coordinates are still retained in the gazetteer, but this data set is now considered archival and will not be updated with new names or changes to approved names.