Office of Geomatics

Enabling GEOINT accuracy through geodetic, geophysical and photogrammetric sciences and content.

"Geodesy remains our life blood"

-- Robert Cardillo, NGA Director
The Director's Intent, 10/3/14
Products and/or services described may only be available to authorized customers.

World Geodetic System 1984 (WGS 84)

The World Geodetic System 1984 (WGS 84) is a 3-dimensional coordinate reference frame for establishing latitude, longitude and heights for navigation, positioning and targeting for the DoD, IC, NATO, International Hydrographic Office and the International Civil Aviation Organization. WGS 84 represents the best global geodetic reference system for the Earth available at this time for practical applications of mapping, charting, geopositioning, and navigation. This standard includes the definition of the coordinate systems fundamental and derived constants, the ellipsoidal (normal) Earth Gravitational Model (EGM), a description of the associated World Magnetic Model (WMM), and a current list of local datum transformations. NGA and the National System for Geospatial-Intelligence (NSG) recommends clicking the following link for further specifications on WGS 84 DoD IT Standards Registry (DISR) (PKI Certs required).


Earth Gravitational Model (EGM)

This division in the Office of Geomatics at NGA is responsible for collecting, processing, and evaluating gravity data (free-air and Bouguer gravity anomalies). These data are then used to compute gravimetric quantities such as mean gravity anomalies, geoid heights, deflections of the vertical, and gravity disturbances. All of these quantities are used in World Geodetic System 1984 support, navigation systems, mapping projects, and different types of surveys.

An Earth Gravitational Model (EGM) is set of geopotential coefficients used in a spherical harmonic expansion to create a global potential surface to coincide with Mean Sea Level (MSL). This surface is called a geoid and it fluctuates above and below the reference ellipsoid surface established by WGS 84. For more information, click on a drop-down menu item above on the EGM tab.

Earth Gravitational Model 2008 (EGM2008)

The EGM84 and EGM96 are legacy products. Users are recommend to use the latest EGM from NGA, currently EGM2008. In 2020, NGA plans to release a new EGM, tentatively named EGM2020, where upon EGM2008 will become a legacy product.

The EGM2008 is provided as a set of normalized, geopotential coefficients complete to degree and order 2159, and contains additional spherical harmonic coefficients extending to degree 2190 and order 2159. Also provided is a 2.5-minute worldwide geoid height file, precomputed from the EGM2008. The coefficient and geoid height files have associated software and documents. EGM2008 was approved for official DoD use as documented in NGA STND.0036_1.0, 2014-07-08.


What's New

April, 2013 - EGM2008 Citation included below with Links to reference EGM2008 and the EGM2008 Erratum are given on left under Additional Information.

EGM2008 Citation: The development and evaluation of the Earth Gravitational Model 2008 (EGM2008) - Nikolaos K. Pavlis, Simon A. Holmes, Steve C. Kenyon, John K. Factor; Journal of Geophysical Research: Solid Earth (1978-2012) Volume 117, Issue B4, April 2012.

May, 2009 - Global 2.5 Minute Geoid Undulation Grid available in GIS format.
February, 2009 - Middle East Geoid Undulation Grid available in GIS format.
February, 2009 - Propagated Error Estimates of EGM2008 released.
January, 2009 - Utility to convert binary files from Big Endian to Small Endian released.
January, 2009 - Gravity Anomalies & Deflections of the Vertical data released.
November, 2008 - SMALL ENDIAN versions of binary files released.
November, 2008 - Files & Products for Oceanographic Applications released.
July, 2008 - WGS 84 version of EGM2008 released. Includes grids and programs for computing geoid undulations relative to WGS 84 Ellipsoid.

Please provide comments, suggestions, and feedback to the contacts below as we strive to improve our EGM2008 products. Thank you!

Dr. Nikolaos Pavlis
NGA, Geodesy and Geophysics Basic and Applied Research
Nikolaos.K.Pavlis@nga.mil
NGA Office of Geomatics (SFN)
EGM 2008 Development Team
Send Email
Earth Gravitational Model 1996 (EGM96)

The EGM84 and EGM96 are legacy products. Users are recommend to use the latest EGM from NGA, currently EGM2008. In 2020, NGA plans to release a new EGM, tentatively named EGM2020, where upon EGM2008 will become a legacy product.

The EGM96 is provided as a set of normalized, geopotential coefficients to degree and order 360. Also provided is a 15-minute worldwide geoid height file, precomputed from the EGM96. The coefficient and geoid height files have associated software and documents. EGM96 was approved for official DoD use as documented in NIMA TR8350.2, Third Edition, 4 July 1997.

Earth Gravitational Model 1984 (EGM84)

The EGM84 and EGM96 are legacy products. Users are recommend to use the latest EGM from NGA, currently EGM2008. In 2020, NGA plans to release a new EGM, tentatively named EGM2020, where upon EGM2008 will become a legacy product.

The EGM84 is provided as a set of normalized, geopotential coefficients to degree and order 180. Also provided is a 30-minute worldwide geoid height file, precomputed from the EGM84. The coefficient and geoid height files have associated software and documents. EGM84 was approved for official DoD use as documented in DMA TR8350.2, Second Edition, 1 September 1991.

World Magnetic Model (WMM)

The World Magnetic Model is the standard model used by the U.S. Department of Defense (DoD), the U.K. Ministry of Defence, the North Atlantic Treaty Organization (NATO) and the International Hydrographic Organization (IHO), for navigation, attitude and heading referencing systems using the geomagnetic field. It is also used widely in civilian navigation and heading systems. The model, associated software, and documentation are distributed by the National Oceanic and Atmospheric Administration (NOAA), National Centers for Environmental Information (NCEI) on behalf of NGA. The model is produced at 5-year intervals. With the current model expiring on December 31, 2019.

Datum Transformations

Data acquired by NGA and referenced to a geodetic datum other than WGS 84 does not meet agency standards, and must therefore undergo a datum transformation to WGS 84.

MSP GEOTRANS

MSP Geotrans is the DoD and IC recognized geographic translator for coordinate conversions and datum transformations.

MSP Geotrans can be downloaded from the Apps & Services tab on the Coordinate Systems page.

List of Documents and Guidance

For assistance setting up geographic translations, acquiring grid system and datum parameters, running batch conversions, and loading MSP Geotrans please refer to materials within the Coordinate Systems Analysis tab.

National System for Geospatial-Intelligence (NSG) Standards

Management of this reference frame falls within the National Systems for Geospatial-Intelligence (GEOINT) (NSG).

Earth Gravitational Model 2008 (EGM2008) Data and Apps

The following links contain documentation, source code, data, and supporting inputs and tools for EGM2008.

File/Link
Description
Zip archive containing all EGM2008 Spherical Harmonics code and documentation.
Zip archive containing all EGM2008 2.5 Minute Interpolation Grid code and documentation.
Earth Gravitational Model 96 (EGM96) Data and Apps

The following links contain documentation, source code, data, and supporting inputs and tools for EGM96.

File/Link
Description
Zip archive containing all EGM96 360 Spherical Harmonics code and documentation.
Zip archive containing all EGM96 15 Minute Interpolation Grid code and documentation.
Online calculator to determine EGM84 geoid height based on latitude and longitude inputs.
Earth Gravitational Model 1984 (EGM84) Data and Apps

The following links contain documentation, source code, data, and supporting inputs and tools for EGM84.

File/Link
Description
Zip archive containing all EGM84 Spherical Harmonics code and documentation.
Zip archive containing all EGM84 30 Minute Interpolation Grid code and documentation.
Online calculator to determine EGM84 geoid height based on latitude and longitude inputs.
World Magnetic Model 2015 - Apps
World Magnetic Model 2015 - Data

The Fortran and C WMM 2015 models can be obtained from NCEI by HTTPS.

Services

Services require PKI certs and allow visualization via the IC Portal or ArcGIS desktop (download). After selecting the link below, additional viewing options may be available by following the link under the "Map Contents" heading.

WGS 84 Resources & Links
Document
Description
Notes

Updated 23 June 2004, changes documented on first page inside front cover.

Change pages for hardcopy of TR8350.2
N/A

NIMA Technical Report TR8350.2, "Department of Defense World Geodetic System 1984, Its Definition and Relationships With Local Geodetic Systems", Third Edition, 4 July 1997 has been amended to correct errata found in the original printing of this edition. There are no changes to the definition of WGS 84 and this does not constitute a "new" WGS 84. Changes are documented inside the front cover of the report. Change pages that can be inserted into hardcopies of the report can also be downloaded.



POINT OF CONTACT
NGA Public Affairs
publicaffairs@nga.mil
Phone: 571-557-5400
Last modified: 07-Dec-17