Richmond77 Project 6057

The magnetic file represents project 6057 only.  It apparently was flown as a fill-in for
the earlier project, 6004, with the intent of combining the two surveys but that did not
occur.  

There are two magnetic and radiometric files representing the two different projects.  The
earliest files are called Richmond-Roanoke74 because the data extends significantly into 
the Roanoke Quadrangle.