MATLAB Examples

# gravity_interp documentation

The gravity_interp function interpolates Antarctic gravity anomalies to arbitary southern- hemisphere coordinates. Data are from Scheinert et al. 2016 and are described below. If you use this function, please cite Scheinert et al. 2016.

## Syntax

```Zi = gravity_interp(lati,loni,varname)
Zi = gravity_interp(xi,yi,varname)
Zi = gravity_interp(...,'method',InterpolationMethod)```

## Description

Zi = gravity_interp(lati,loni,varname) interpolates the field varname, which can be 'ellipsoidal height', 'orthometric height', 'free air', 'accuracy', or 'bouger anomaly', to any point, line, or grid given by the geo coordinates lati, loni.

Zi = gravity_interp(xi,yi,varname) interpolates varname to polar stereographic (ps71) coordinates, where xi and yi are in meters. PS71 coordinates are automatically determined by the islatlon function.

Zi = gravity_interp(...,'method',InterpolationMethod) specifies an interpolation method. Can be any method accepted by the interp2 function. Default InterpolationMethod is 'linear'.

## Requirements

To use the gravity_interp function you'll need the antgg2015.nc data file. If the gravity_data function cannot find antgg2015.nc, it'll try to download the data automatically. If you prefer to download the data manually you can get it here: http://hs.pangaea.de/Maps/antgg2015/antgg2015.nc

## Example

Interpolate free air gravity anomalies to a 1 km resolution grid centered on Larsen Ice Shelf. First use psgrid to create a grid a 1000-km wide grid, then interpolate to geo coordinates.

```[lat,lon] = psgrid('larsen ice shelf',1000,1); FA = gravity_interp(lat,lon,'free air'); ```

If you have Matlab's Mapping Toolbox you can plot in geo coordinates quite easily. If you do not have Matlab's Mapping Toolbox, check out pcolorps in the AMT package for alternate plotting options.

```mapzoom('larsen ice shelf','inset','ne') pcolorm(lat,lon,FA) bedmap2 gl bedmap2 coast ```

## Data citation

If you use this data, please cite the following:

Citation: Scheinert, M et al. (2016): Antarctic free-air and complete Bouguer gravity anomaly grid. doi:10.1594/PANGAEA.848168,

Supplement to: Scheinert, Mirko; Ferraccioli, Fausto; Schwabe, Joachim; Bell, Robin E; Studinger, Michael; Damaske, Detlef; Jokat, Wilfried; Aleshkova, Nadezhda D; Jordan, Tom A; Leitchenkov, German L; Blankenship, Donald D; Damiani, Theresa; Young, Duncan A; Cochran, James R; Richter, Thomas (2016): New Antarctic Gravity Anomaly Grid for Enhanced Geodetic and Geophysical Studies in Antarctica. Geophysical Research Letters, online first, doi:10.1002/2015GL067439

Abstract: Gravity surveying is challenging in Antarctica because of its hostile environment and inaccessibility. Nevertheless, many ground-based, airborne and shipborne gravity campaigns have been completed by the geophysical and geodetic communities since the 1980s. We present the first modern Antarctic-wide gravity data compilation derived from 13 million data points covering an area of 10 million km^2, which corresponds to 73% coverage of the continent. The remove-compute-restore technique was applied for gridding, which facilitated levelling of the different gravity datasets with respect to an Earth Gravity Model derived from satellite data alone. The resulting free-air and Bouguer gravity anomaly grids of 10 km resolution are publicly available. These grids will enable new high-resolution combined Earth Gravity Models to be derived and represent a major step forward towards solving the geodetic polar data gap problem. They provide a new tool to investigate continental-scale lithospheric structure and geological evolution of Antarctica.

## Author Info:

This function and supporting documentation were written by Chad A. Greene of the University of Texas at Austin's Institute for Geophysics (UTIG) in January of 2016. I did not generate to the dataset nor contribute to the GRL manuscript. If you use this function, please give credit where credit is due and cite Scheinert et al. as described above.