Survey number: 550 (Pat Hill number)
Name: Alaska Regional (Aeromagnetic Map of Northeastern Alaska)
Date flown: July and August 1965 (also includes data from 1954 and 1958)
Company: USGS
Flight specs: approx. 10 mile flightline spacing, north-south, mostly
              5000 ft barometric (higher in some mountainous regions).
Instrument: continuous recording flux-gate magnetometer (analog)

Digitized by: DIGIMAP (Esther Castellanos, December 1996)
Map scale: 1:1,000,000

Datum: arbitrary datum, no diurnal corrections, regional field removed

       ("The gradient removed was represented by linear contours trend-
         ing N 25 W so spaced that the gradient decreased from about
         4 gammas per mile at the southwest corner of the map to about
         3 gammas per mile at the northeast corner."
         USGS Bulletin 1271-F, p. F5)

Publication:  Geologic Interpretation of Reconnaissance Aeromagnetic Survey
              of Northeastern Alaska, by William P. Prosge, Earl E. Brabb, and 
              Elizabeth R. King, 1970, U.S. Geological Survey Bulletin
              1271-F, 14 pages, 3 plates (scale 1:1,000,000).

Data format: Ascii format, XYZ records 
             Longitude (degrees), Latitude (degrees), Total Field (nT)
             written with FORTRAN format: (f10.5,x,f10.5,x,f8.1)

Background: These data were digitized under the direction of Rick Saltus 
            (saltus@usgs.gov) as part of the USGS project to merge the best 
            available aeromagnetic data into a consistent grid for the state 
            of Alaska.