Georgia Aeromagnetic Data
The assembly of the 14 individual aeromagnetic surveys
and grids to create the Georgia State-wide compilation was done in several
GENERAL DATA PROCESSING STEPS (not all steps were
applied to this State)
- Grids were constructed from the original
aeromagnetic survey data with a cell size of between 1/3 and 1/5 of the
flightline spacing of the survey, using a minimum curvature gridding
algorithm. For digitized contour line data, the initial grid was constructed
using a minimum curvature algorithm and a spacing appropriate for the scale
of the digitized map.
- The Definitive Geomagnetic Reference Field (DGRF)
calculated for the date and elevation of the original survey was subtracted
(in some cases this required the determination and removal of the original
reference field applied).
- Flightlines were adjusted and spurious anomalies
(generated by equipment malfunction) were removed as necessary.
- Strike filtering in the direction of the flightlines
was applied as necessary.
- The survey grids were regridded, as necessary, to
the final grid cell size of 500 m using a minimum curvature algorithm.
- The original survey grids were continued to 1000 ft
above ground, if necessary, and converted from level to drape as necessary.
Upward continuation of the NURE surveys was by standard 2D FFT filtering
- The datum levels of the converted grids were
adjusted (by addition or subtraction of a constant value) to minimize
differences at the boundaries.
- These adjusted grids were combined into a single
merged grid that shows the magnetic field measured or calculated at 1000 ft
above ground. Weighted averaging of the data was applied in the
GRID PROJECTION SPECIFICATIONS
- Projection = Lambert conformal conic
- Central meridian = 81 degrees W
- Base latitude = 0 degrees N
- Standard parallels = 33 and 45 N
- Semi-major ellipsoid axis = 6378206.4 m
- Eccentricity squared = 0.0067686579973
Mag || USGS - Eastern Minerals Team
|| USGS - Geology || USGS
U.S. Department of the Interior, U.S. Geological Survey
This page is https://pubs.usgs.gov/openfile/of01-106/proc.htm
Contact: David L. Daniels
Maintained by Eastern Region Publications Web Team
Last updated 09 April 2001