These datasets were prepared at the invitation of the Solid Earth Geophysics Division of the National Geophysical Data Center (NGDC), NOAA, for inclusion in their new revision of the Gravity CD-ROM. Our grids are also being made available to the pub GEOID GEOID96lic through this index page. However, we strongly encourage users to consider obtaining the new Gravity CD-ROM when it is available, since it will include access software, as well as many other data sets.
The grids below are offered "as is", and were made to assist various research activites. We can not offer any support software to access these data. However, the data are written in a very straightforward fashion. eAch individual element of the grid is written in ASCII, one value per line. Each line (or record) is 8 characters wide (not counting carriage return or line-feed). The data are written as signed real numbers with a decimal point and three digits after the decimal. The grids are compressed. The uncompressed versions are significantly larger in size when uncompressed. For example, the grids for the conterminous United States will uncompress to almost 16.5 Mbytes.
The grid descriptions are short summaries detailing background information. The format files are written in a specific fashion to conform to NGDC requirements. An example of the format for the GEOID96 model for the conterminous United States is shown below:
file_title = u.s. geoid heights (geoid96) upper_map_y = 53 lower_map_y = 24 left_map_x = -130 right_map_x = -66 number_of_rows = 871 number_of_columns = 1921 grid_size(x) = 0.03333333333333333 grid_size(y) = 0.03333333333333333 grid_unit = degree grid_origin = lowerleft grid_sequence = left_right_up map_projection = lat/lon data_value_unit = meters
As seen from the information above, the GEOID96 geoid height grid for the conterminous United States contains 1,673,191 records. The data begin in the southwest corner of the grid (lower left), progress to the southeast corner of the grid (lower right), and continue row-wise, south to north.
Geoid Height
| Conterminous U.S. (GEOID96) | ZIP [4200K] | Description | Format |
| Alaska | ZIP [1605K] | Description | Format |
| Hawaiian Islands | ZIP [90K] | Description | Format |
| Puerto Rico and Virgin Islands | ZIP [51K] | Description | Format |
| Mexico (MEXICO97 model) | ZIP [1968K] | Description | Format |
Deflection of the Vertical, N/S Component
| Conterminous U.S. (DEFLEC96) | ZIP [4242K] | Description | Format |
| Alaska | ZIP [1691K] | Description | Format |
| Hawaiian Islands | ZIP [105K] | Description | Format |
| Puerto Rico and Virgin Islands | ZIP [59K] | Description | Format |
| Mexico (DMEX97 model) | ZIP [1975K] | Description | Format |
Deflection of the Vertical, E/W Component
| Conterminous U.S. (DEFLEC96) | ZIP [4385K] | Description | Format |
| Alaska | ZIP [1680K] | Description | Format |
| Hawaiian Islands | ZIP [104K] | Description | Format |
| Puerto Rico and Virgin Islands | ZIP [57K] | Description | Format |
| Mexico (DMEX97 model) | ZIP [2013K] | Description | Format |
Terrrain Corrected Free-Air Gravity Anomalies
| Conterminous U.S. | ZIP [5232K] | Description | Format |
| Alaska | ZIP [2034K] | Description | Format |
| Hawaiian Islands | ZIP [125K] | Description | Format |
| Puerto Rico and Virgin Islands | ZIP [72K] | Description | Format |
| Mexico | ZIP [3165K] | Description | Format |
Number of Gravity Data per Cell
| Conterminous U.S. | ZIP [581K] | Description | Format |
| Alaska | ZIP [168K] | Description | Format |
| Hawaiian Islands | ZIP [15K] | Description | Format |
| Puerto Rico and Virgin Islands | ZIP [5K] | Description | Format |
| Mexico | ZIP [318K] | Description | Format |
| Conterminous U.S. | ZIP [4199K] | Description | Format |