Montana Aeromagnetic Data Processing
The assembly of 65 individual aeromagnetic surveys and grids to
build the Montana state-wide compilation was done in several
Montana mag ||
DATA PROCESSING STEPS
- 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 when necessary
due to wide flightline spacing. 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.
- Data quality problems were addressed.
- The Definitive Geomagnetic Reference Field (DGRF) was applied for
the date of the original survey (in some cases this required the
determination and removal of the original reference field applied).
- The survey grids were regridded, as necessary, to the final
grid cell size of 500 m using a minimum curvature algorithm.
- The datum levels of adjacent surveys were adjusted (by addition
or subtraction of a constant value) to minimize differences at the
- The original survey grids were upward or downward
continued and converted from level to drape as necessary to
produce a consistent survey specification of 1000 ft above ground.
Upward continuation of the NURE surveys was by standard 2D FFT
filtering techniques. Downward continuation and level-to-drape
was performed (Cordell and others, 1992).
- The datum levels of the converted grids were then adjusted
to minimize differences at the boundaries.
- These adjusted grids were combined into a single merged grid.
GRID PROJECTION SPECIFICATIONS
- Projection = Lambert conformal conic
- Central meridian = 110 degrees W
- Base latitude = 0 degrees N
- Standard parallels = 33 and 45 degrees N
- Semi-major ellipsoid axis = 6378206.4 m
- Eccentricity squared = 0.0067686579973
U.S. Department of the Interior
U.S. Geological Survey
This page is <URL: https://pubs.usgs.gov/of/1998/ofr-98-0333/mt_proc.html>
Site Maintainers: Joan Nadeau and Gene
For more information about this report contact: Anne McCafferty
Last updated 07 Dec 2016