The Decade of North American Geology (DNAG) gravity grid values, spaced at 6 km, were used to produce the Gravity Anomaly Map of North America (1987; scale 1:5,000,000). Considerable caution should be exercised when using these gridded data in regions of sparse coverage (for example, deep oceanic areas). The spatial distribution of the original data from which the grid was generated is shown on sheet 5 of the published map. Note: There are no gridded data values for Mexico.

The gravity station data (1,522 records) were compiled by the Portland State University. This data base was received in August 1990. Principal gravity parameters include Free-air Anomalies and Complete Bouguer Anomalies (terrain correction applied). The observed gravity values are referenced to the International Gravity Standardization Net 1971 (IGSN 71). The gravity anomaly computation uses the Geodetic Reference System 1967 (GRS 67) theoretical gravity formula. The data are randomly distributed within the boundaries of the greater Portland area.

The gravity station data (55,907 records) were gathered by various governmental organizations (and academia) using a variety of methods. This data base was received in March 1993. Principal gravity parameters include Free-air Anomalies and Simple Bouguer Anomalies (no terrain correction applied). The observed gravity values are referenced to the International Gravity Standardization Net 1971 (IGSN 71) and the gravity anomaly computation uses the Geodetic Reference System 1967 (GRS 67) theoretical gravity formula. The spatial resolution of the data is randomly distributed within the boundaries of Minnesota.

The Central Andes gravity data (6,151 records) were compiled by Professor Gotze and the MIGRA Group. This data base was received in April, 1997. Principal gravity parameters include Free-air Anomalies and Bouguer Anomalies (terrain and mass corrected). The gravity station data have been adjusted to the International Gravity Standardization Net 1971 (IGSN 71). The gravity anomaly computation uses the Geodetic Reference System 1967 (GRS 67) theoretical gravity formula. The data are randomly distributed within the area bounded by 64 - 71 degrees West and 20 - 29 degrees South in the Central Andes of South America.

The gravity station data (10,578 records) were compiled by the U.S. Geological Survey and the State of Alaska Division of Geological & Geophysical Surveys. This data base was received in February, 1993. Principal gravity parameters include Free-air anomalies, isostatic anomalies and Simple Bouguer anomalies (no terrain correction applied). The "wpn" suffix indicates that a crustal thickness of 30 kilometers was used in the isostatic calculation. The observed gravity values are referenced to the International Gravity Standardization Net 1971 (IGSN 71). The gravity anomaly computation uses the Geodetic Reference System 1967 (GRS 67) theoretical gravity formula. Note that the original USGS Open File Report by D. F. Barnes mentions the use of the 1931 International Ellipsoid for gravity reduction but this is believed to have subsequently been changed to the GRS 67 system.

The gravity station data (24,284 records) were compiled by the U. S. Geological Survey. This data base was received on February 23, 1993. Principal gravity parameters include observed gravity, Free-air anomalies and Bouguer anomalies. The observed gravity values are referenced to the International Gravity Standardization Net 1971 (IGSN 71). The gravity anomaly computation uses the Geodetic Reference System 1967 (GRS 67) theoretical gravity formula.

The gravity station data (3814 records) were compiled by Professor Ervin. This data base was received in April 1993. Principal gravity parameters include Free-Air Anomalies and Simple Bouguer Anomalies (no terrain correction applied). The observed gravity values are referenced to the International Gravity Standardization Net 1971 (IGSN 71). The gravity anomaly computation uses the Geodetic Reference System 1967 (GRS 67) theoretical gravity formula. The data are randomly distributed within the area of northwestern Wisconsin north of 45 degrees north latitude.

A 2 kilometer Bouguer anomaly grid for the state of Maine. Number of columns is 197 and number of rows is 292. The order of the data is from the lower left to the right and then up one row.

A 2.5 kilometer Bouguer anomaly grid for the state of Utah. Number of columns is 196 and number of rows is 245. The order of the data is from the lower left to the right and then up one row.

The gravity station data (72,677 records) were compiled by the U.S. Geological Survey and the State of Alaska Division of Geological & Geophysical Surveys. This data base was received in February, 1993. Principal gravity parameters include Free-air anomalies, isostatic anomalies and Simple Bouguer anomalies (no terrain correction applied). The "iso" suffix indicates that a crustal thickness of 25 kilometers was used in the isostatic calculation. The observed gravity values are referenced to the International Gravity Standardization Net 1971 (IGSN 71). The gravity anomaly computation uses the Geodetic Reference System 1967 (GRS 67) theoretical gravity formula. Note that the original USGS Open File Report by D. F. Barnes mentions the use of the 1931 International Ellipsoid for gravity reduction but this is believed to have subsequently been changed to the GRS 67 system.