# Earth2014

- freely available via http://ddfe.curtin.edu.au/models/Earth2014/
- folder GMT has data in wikipedia:Generic Mapping Tools format

The Earth2014 global topography and relief model provides layered topography grids at 1 arc-minute resolution. Other than SRTM30plus, Earth2014 provides information on ice-sheet heights and bedrock (that is, topography below the ice) over Antarctica and Greenland

SRTM30_PLUS v9 (Becker et al. 2009) bathymetry over the oceans and major inland lakes, and over land in high northern latitudes (except for Greenland)... The RET-layer (also denoted RET2014) models ice, water and rock masses based on a uniform mass-density of 2670 kg/m3... a constant value of 6,371,000 m has been subtracted from all shape models... land types as follows: 0 - land topography above mean sea level (MSL), 1 - land topography below MSL, 2 - ocean bathymetry, 3 - inland lake, bedrock above MSL, 4 - inland lake, bedrock below MSL, 5 - ice cover, bedrock above MSL, 6 - ice cover, bedrock below MSL, 7 - ice shelf, 8 - ice covered lake (Vostok)... For use of Earth2014 in #spectral modelling, sets of fully-normalized (4pi) SHCs complete to degree and order 10,800 were derived from the 1 arc-min grids... SHCs are stored in Curtin University's binary SHC (bshc)-format in "double precision". The bshc-format holds the data as follows: n_min n_max C-coefficients ascending in degree, followed by the order, S-coefficients ascending in degree, followed by the order

## Contents

# geoid[edit | edit source]

## geoid undulations[edit | edit source]

## geoid undulations in units of gravity[edit | edit source]

geoid undulations, using units of gravity Spherical harmonics are often used to approximate the shape of the geoid. The current best such set of spherical harmonic coefficients is EGM96... equation describes the Earth's gravitational potential V, not the geoid itself

# models[edit | edit source]

## relief[edit | edit source]

## shape model[edit | edit source]

shape models represent the geometry of the planet via the planetary radius... These were obtained as sum of ellipsoidal radii of the the GRS80 ellipsoid, EGM96 geoid undulations, and the elevations

geoid undulations in HEALPix resolution k=10 (12,6 millions of cells) are limited from -108.1 m to +85 m

## issues[edit | edit source]

5 arc min Earth shapes in HEALPix projection are visually distorted ,

but in native Latitude-Longitude are visually normal .

If to look on 1 arc min shapes then situation is opposite

- picture is visually correct in HEALPix projection

but in native Latitude-Longitude is distorted .

# resolutions[edit | edit source]

## 5 arc-min[edit | edit source]

## 1 arc-min[edit | edit source]

# spectral modelling[edit | edit source]

with the fully normalized SHCs Tnm of degree n and order m (m<0: sine associated; m≥0: cosine associated), the elevation H of the topography model can be retrieved at any point on Earth, given by geocentric latitude and longitude . Ynm denote the spherical harmonic functions that evaluate the associated Legendre functions (ALFs) depending on the co‐latitude, and sine / cosine arguments depending on longitude... If full topographic information is sought, the data grids should be used instead of the spherical harmonic representations.