This 2' geoid height grid for the Principal Hawaiian Islands is distributed as a GEOID96 model. The computation used 61,000 terrestrial and marine gravity data held in the National Geodetic Survey gravity data base in July 1996. These data were augmented by gravity data contributions from NGA (former National Imagery and Mapping Agency (former Defence Mapping Agency)). By means of a Fast Fourier Transform (FFT) technique, high frequency corrections were made to an underlying EGM96 geopotential model through a remove, compute, and restore process. The gravity values are based on the International Gravity Standardization Net 1971 (IGSN71). The geoid heights are referred to the Geodetic Reference System 1980 (GRS80) ellipsoid. Unlike the grid for the conterminous United States, this GEOID96 grid does not incorporate GPS on leveled benchmarks. This model is a gravimetric geoid in a geocentric, ITRF94(1996.0) reference frame. It is necessary to subtract 12.0 cm from these values to obtain the geoid undulation between the best-fit global geopotential surface and the GRS80 ellipsoid (both expressed in a tide free system). Additional information is available at: http://www.ngs.noaa.gov/GEOID/geoid.html We are particularly grateful to NGA (former National Imagery and Mapping Agency) for their assistance and their data contributions.

This 2' surface deflection of the vertical grid for the Principal Hawaiian Islands is the DEFLEC96 model. The computation used about 61,000 terrestrial and marine gravity data held in the National Geodetic Survey gravity data base in July 1996. These data were augmented by gravity data contributions from NGA (former National Imagery and Mapping Agency (former Defence Mapping Agency)). The deflections were obtained by numerical differentiation of cubic spline models along the meridians of the GEOID96 grid. The gravity values are based on the International Gravity Standardization Net 1971 (IGSN71). The deflections are referred to the Geodetic Reference System 1980 (GRS80) ellipsoidal normals. The curvature of the plumb line correction has been applied. We are particularly grateful to NGA (former National Imagery and Mapping Agency) for their assistance and their data contributions.

This 2' surface deflection of the vertical grid for the Principal Hawaiian Islands is the DEFLEC96 model. The computation used about 61,000 terrestrial and marine gravity data held in the National Geodetic Survey gravity data base in July 1996. These data were augmented by gravity data contributions from NGA (former National Imagery and Mapping Agency (former Defence Mapping Agency)). The deflections were obtained by numerical differentiation of cubic spline models along the parallels of the GEOID96 grid. The gravity values are based on the International Gravity Standardization Net 1971 (IGSN71). The deflections are referred to the Geodetic Reference System 1980 (GRS80) ellipsoidal normals. The curvature of the plumb line correction has been applied. We are particularly grateful to NGA (former National Imagery and Mapping Agency) for their assistance and their data contributions.

This 2' gravity density grid for Puerto Rico and the Virgin Islands displays the distribution of about 26,000 terrestrial and marine gravity data held in the National Geodetic Survey gravity data base in July 1996. These data were augmented by gravity data contributions from NGA (former National Imagery and Mapping Agency (former Defence Mapping Agency)) and by satellite altimeter-derived marine gravity anomalies computed by Sandwell and Smith (1996). The values show the number of gravity data contained in a given 2' cell. Additional information is available at http://www.ngs.noaa.gov/GEOID/geoid.htmlWe are particularly grateful to NGA (former National Imagery and Mapping Agency) for their assistance and their data contributions.

This 2' gravity density grid for the conterminous United States displays the distribution of the about 1.8 million terrestrial and marine gravity data held in the National Geodetic Survey gravity data base in July 1996. These data were augmented by gravity data contributions from NGA (former National Imagery and Mapping Agency (former Defence Mapping Agency)) and by satellite altimeter-derived marine gravity anomalies computed by Sandwell and Smith (1996). The values show the number of gravity data contained in a given 2' cell. Additional information is available at http://www.ngs.noaa.gov/GEOID/geoid.htmlWe are particularly grateful to NGA (former National Imagery and Mapping Agency) for their assistance and their data contributions.

This 2' gravity anomaly grid for the Principal Hawaiian Islands is NOT the input data set used in development of the GEOID96 model. This gravity grid models the 61,000 terrestrial and marine gravity data held in the National Geodetic Survey gravity data base in July 1996. The data used in this grid have NOT been augmented by gravity data contributions from NGA (former National Imagery and Mapping Agency (former Defence Mapping Agency)). Please note that the GEOID96 model itself does contain the NGA (former National Imagery and Mapping Agency) contributions. These gravity values are based on the International Gravity Standardization Net 1971 (IGSN71). Terrain corrected, atmospherically corrected, Bouguer anomalies were computed with respect to the Geodetic Reference System 1980 (GRS80) using NAD83 and NAVD88 coordinates. Terrain corrections were computed by an FFT method from 6" digital elevation data. These complete Bouguer anomalies were gridded by splines in tension. The free air anomaly grid was obtained by restoring the Bouguer plate with a 2' mean elevation grid. Additional information is available at: http://www.ngs.noaa.gov/GEOID/geoid.html

This data set includes gravity measurements for the Island of Hawai`i collected as the source data for "Deep magmatic structures of Hawaiian volcanoes, imaged by three-dimensional gravity models" (Kauahikaua, Hildenbrand, and Webring, 2000). Data for 3,611 observations are stored as a single table and disseminated in .CSV format. Each observation record includes values for field station ID, latitude and longitude (in both Old Hawaiian and WGS84 projections), elevation, and Observed Gravity value. See associated publication for reduction and interpretation of these data.

This data set includes gravity measurements for the Island of Hawai`i collected as the source data for "Deep magmatic structures of Hawaiian volcanoes, imaged by three-dimensional gravity models" (Kauahikaua, Hildenbrand, and Webring, 2000). Data for 3,611 observations are stored as a single table and disseminated in .CSV format. Each observation record includes values for field station ID, latitude and longitude (in both Old Hawaiian and WGS84 projections), elevation, and Observed Gravity value. See associated publication for reduction and interpretation of these data.

This 2' gravity density grid for Mexico, North-Central America, and the Western Caribbean Sea shows the distribution of about one million terrestrial and marine gravity measurements held in the NGS database as of March 1997. These gravity measurements have been augmented by data contributions from NGA (former National Imagery and Mapping Agency), and satellite altimeter-derived gravity anomalies computed by Sandwell and Smith (1997). This density grid shows the number of gravity data contained in a 2' x 2' cell. Please note that this coverage grid does not show the 15'x15' EGM96 gravity values used to fill the void areas south of 20 degrees North. Additional information is available at: http://www.ngs.noaa.gov/GEOID/MEXICO97 .We are particularly grateful to NGA (former National Imagery and Mapping Agency) for their assistance and their data contributions.

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.