New mean field

You can download the new mean gravity field EIGEN-6S2 which results from the cooperation between GFZ (GeoForschungsZentrum, Potsdam) and CNES/GRGS on the « EIGEN » series of models. This model is proposed for the ITRF2013 standards.

EIGEN-6S2 is complete to degree and order 260. It is based on a GFZ internal GRACE+GOCE solution for the part between degree 51 and 260. The time-variable gravity (TVG) coefficients between degrees 2 and 50 are obtained from a regression on the GRGS-RL02 10-day time series (2003-2012). For degree 2 this TVG part is extended to 1985-2012 through the use of a GRGS SLR-only (Lageos+Lageos-2) solution between 1985 and 2003.

Outside of the measurements period (1985-2012 for degree 2, 2003-2012 for degrees 3 to 50), the gravity field is extrapolated with a zero-slope assumption.

The new modeling of the TVG part includes:

  • Two annual and two semi-annual coefficients
  • One bias and one drift for each year. (Note that the reference date of the bias is the beginning of the period of validity of the coefficient, i.e. the beginning of the year in most cases, see format). The bias and drift are in general coherent so that the result is a piece wise linear function, except in the case of earthquakes

The extended GRACE format is an extension of the official GRACE format for gravity fields. An explanation of the format is given here.

EIGEN-6S2 can also be downloaded in ICGEM-V2 format from here.

It is possible with our interactive tools to compute a static gravity field at any given date from this model.

In addition, you will find two software packages in Fortran90:

  • a GRACE to ICGEM-V2 (and vice versa) format converter: here
  • a kit to compute the gravity field at any given date from the new extended GRACE format: here