Directory Title: Alaska North-South Deflections (DEFLEC96) 
Principal Investigator: Dr. Dennis G. Milbert
Contributing Organization: NOAA, National Geodetic Survey, N/NGS5
                           1315 East-West Highway, Room 9349
                           Silver Spring, MD 20910-3282
                           dennis@ngs.noaa.gov

Summary:  This 2' x 4' surface deflection of the vertical grid for 
Alaska is the DEFLEC96 model.  The computation used about 1.1 
million terrestrial and marine gravity data held in the National 
Geodetic Survey gravity data base in July 1996.  These data were 
augmented by gravity data contributions from NIMA (former Defense 
Mapping Agency).  The deflections were obtained by numerical 
differentiation of cubic spline models along the meridians of the 
GEOID96 grid.  The gravity values are based on the International 
Gravity Standardization Net 1971 (IGSN71).  The deflections are 
referred to the Geodetic Reference System 1980 (GRS80) ellipsoidal 
normals.  The curvature of the plumb line correction has been 
applied.  Additional information is available at: 
http://www.ngs.noaa.gov/DEFLEC/deflec.html We are particularly 
grateful to NIMA for their assistance and their data contributions.