Denver Project 6048B & 6049B

This quad was flown from about September 1977 to October 1977
and August 1978.  Both fixed-winged and rotary-winged aircraft
were used in both years.  From the report, it states the
eastern portion was flown with a fixed-wing in 1978 and 
the west portion was flown with a rotary-wing in 1977.  

To add to the confusion, beginning in the fall of 1978, the original 
contractor took all the data from both aircrafts and both years and 
combined them.  The lines were probably renumbered at that time.  
A Julian date was given for the whole line even though portions may 
have been flown in different years and most likely on different days 
of the month.  We were not able to label each line with the year
in which it was flown so we selected 1978 for all the lines.  

The original publication may provide further clarification:

GeoMetrics, Inc., 1979, Aerial gamma ray and magnetic survey, 
Rockies/Laramie Range project, Denver and Pueblo quadrangles, 
Colorado: U.S. Dept. Energy, Grand Junction Office 
Rept. GJBX-049(79), 3 vol.