Two basic types of terrain are present, maria and terrae. Basin and crater materials compose most of the terrae. The maria, of volcanic origin, are concentrated in the basins and in their peripheral troughs. All attributes created during the creation process were verified by displaying the lines in both the database and the spatial coverage, but no formal tests were performed.
Line geometry is topologically clean.
Geology mapped 1971-72. Brightness data from Apollo 8 and Apollo 17 Hasselblad frames taken during trans-Earth coast. Information has been obtained from sources believed to be reliable, but its accuracy and completeness and the opinions based thereon, are not guaranteed. As every effort is made to provide accurate information in this database, USGS would appreciate it if users could call to our attention any errors that may occur by communicating with the contact person.