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Data Series 411

Michigan Complete Bouguer Gravity Anomaly Map

Previous gravity maps of Michigan and the Great Lakes were published by Klasner and others (1979) and O'Hara (1981). The complete Bouguer gravity anomaly grid used to make the contour map below was compiled from 33 different gravity surveys that total 20,412 gravity measurements. Surveys with fewer than 5 stations within Michigan were discarded. Bouguer anomaly values were interpolated into a grid with 2,500 meter interval. Table 2 lists the surveys giving the National Geospatial and Imaging Agency (NGA) survey code, and the number of stations within Michigan used from each survey. Land gravity data came from the University of Texas-El Paso (UTEP) / PACES research center database. The three Great Lakes surveys (#3235 Lake Superior, #3974 Lake Michigan, and #3738 Lake Huron) are listed separately at the end of Table 2. These three surveys were obtained from the National Geophysical Data Center (NGDC) CD-ROM (Dater and others, 1999). 

Observed gravity measurements relative to the International Gravity Standardization Net 1971 (IGSN-71 datum (Morelli, 1974; Defense Mapping Agency, 1974) were reduced to the complete Bouguer anomaly using the 1967 gravity formula (International Union of Geodesy and Geophysics, 1971) and a reduction density of 2.67 grams per cubic centimeter. Data were collected in Lake Superior and the southern part of Lake Michigan using LaCoste-Romberg geodetic underwater gravity meters on the lake bottom by Wold and Berkson (1977), whereas data were collected in Lake Huron and the northern part of Lake Michigan with ship gravimeters at the lake surface (O'Hara, 1981). Terrain corrections were made only for the land measurements and were calculated radially outward from each station to a distance of 167 kilometers, using a method developed by Plouff (1977).  Accuracy of the lake survey data is less than the land survey data.

Map below shows the Michigan complete Bouguer gravity anomaly

 

Gravity Grid Projection Specifications

  • Projection = Lambert conformal conic
  • Central meridian = 84 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
  • Horizontal datum = NAD27
  • Ellipsoid = Clarke 1866
Revised March 7, 2018

Posted March 2009

For more information about this report contact: Steve Snyder.

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Page Last Modified: Wednesday, March 07, 2018, 01:15:43 PM