This calculates the value of gravity based on latitude and elevation above sea level.
The Geodetic Reference System 1967
Woollard G.P. 1979 “The new gravity system – changes in international gravity base values and anomaly values” Geophysics, 44 1352 – 1366
IAG Developed Geodetic Reference System 1980, leading to World Geodetic Reference System 1984 (WGS84)
Kelton calculation reference C025
FLOCALC calculation reference F025
- IGF 1967
Calculation is performed in accordance with the Geodetic Reference System 1967
- Wollard 1979
Calculation is performed in accordance with the formulae given in Woollard G.P. 1979 “The new gravity system – changes in international gravity base values and anomaly values” Geophysics, 44 1352 – 1366.
- IAC 1980/ WGS 1984
Calculation is performed in accordance with the IAG Developed Geodetic Reference System 1980, leading to World Geodetic Reference System 1984 (WGS84)
Use this option for calculating gravity for an offshore location
This gives the option of making an additional correction for the density of the rock base
All calculations are performed in SI units unless otherwise stated, the formulae use the geographic latitude in radians.
Calculation of gravity at sea level
IAC 1980/ WGS 1984
|λ||=||Geographic latitude in radians|
The effect of elevation allows for the ‘free-air’ gradient of gravity given by Newtons Law of Gravity, and Bouguer slab effect resulting from the layer of rock between sea-level datum and the site.
|ρr||=||Density of the rock|
|e||=||Elevation above sea level|
A small effect for height above ground level of the site (i.e. bench height) involving the free air gradient alone
|h||=||Height above ground level|
Bouguer Gravity Anomaly B
The Bouguer gravity anomaly depends upon the distribution of the underlying rocks anc can only be determined by measurement.
The value of local gravity can be calculated by