geoidheight - Calculate geoid height

Syntax

N = geoidheight(latitude,longitude) N = geoidheight(latitude, longitude, modelname) N = geoidheight(latitude, longitude, action) N = geoidheight(latitude, longitude, modelname, action) N = geoidheight(latitude, longitude, 'Custom', datafile) N = geoidheight(latitude, longitude, 'Custom', datafile, action)

Description

N = geoidheight(latitude,longitude) calculates the geoid height using the EGM96 Geopotential Model. For this model, it calculates these geoid heights to an accuracy of 0.01 m. It interpolates an array of m geoid heights at m geocentric latitudes, latitude, and m geocentric longitudes, longitude.

N = geoidheight(latitude, longitude, modelname) calculates the geoid height using the model, modelname.

N = geoidheight(latitude, longitude, action) calculates the geoid height using the EGM96 Geopotential Model. This function performs action if latitude or longitude are out of range.

N = geoidheight(latitude, longitude, modelname, action) calculates the geoid height using modelname.

N = geoidheight(latitude, longitude, 'Custom', datafile) calculates the geoid height using a custom model that datafile defines.

N = geoidheight(latitude, longitude, 'Custom', datafile, action) calculates the geoid height using the custom model. This function performs action if latitude or longitude are out of range.

Tips

This function interpolates geoid heights from a grid of point values in the tide-free system.
When using the EGM96 Model, this function has the limitations of the 1996 Earth Geopotential Model.
When using the EGM2008 Model, this function has the limitations of the 2008 Earth Geopotential Model.
The interpolation scheme wraps over the poles to allow for geoid height calculations at and near pole locations.
The geoid undulations for the EGM96 and EGM2008 models are relative to the WGS84 ellipsoid.
The WGS84 EGM96 geoid undulations have an error range of +/– 0.5 to +/– 1.0 m worldwide.

Input Arguments

latitude

An array of m geocentric latitudes, in degrees, where north latitude is positive and south latitude is negative. latitude must be of type single or double. If latitude is not within the range –90 to 90, inclusive, this function wraps the value to be within the range.

longitude

An array of m geocentric longitudes, in degrees, where east longitude is positive and west longitude is negative. longitude must be of type single or double. If longitude is not within the range 0 to 360 inclusive, this function wraps the value to be within the range.

model

String that specifies the geopotential model.

Geopotential Model Description

'EGM96'
EGM96 Geopotential Model to degree and order 360. This model uses a 15-minute grid of point values in the tide-free system. This function calculates geoid heights to an accuracy of 0.01 m for this model.

'EGM2008'
EGM2008 Geopotential Model to degree and order 2159. This model uses a 2.5-minute grid of point values in the tide-free system. This function calculates geoid heights to an accuracy of 0.001 m for this model.

'Custom'
Custom geopotential model that you define in datafile. This function calculates geoid heights to an accuracy of 0.01 m for custom models.
Note To deploy a custom geopotential model, explicitly include the custom data and reader files to the MATLAB Compiler™ (mcc) command at compilation. For example:
mcc -m mycustomsgeoidheightfunction... -a customDataFile -a customReaderFile
For other geopotential models, use the MATLAB Compiler as usual.

Default: EGM96

datafile

Optional file that contains definitions for a custom geopotential model. Provide this file only if you specify 'Custom' for the model argument. For an example of file content, see aerogmm2b.mat.

This file must contain the following variables.

Variable Description

'latbp'
Array of geocentric latitude breakpoints.

'lonbp'
Array of geocentric longitude breakpoints.

'grid'
Table of geoid height values.

'windowSize'
Even integer scalar greater than 2 for the number of interpolation points.

action

String that defines action for out-of-range input. Specify one:

'Error'

'Warning'

'None'

Default: Warning

Output Arguments

`N`	An array of `M` geoid heights in meters. The values in this array have the same data type as `latitude`.

Examples

Calculate the EGM96 geoid height at 42.4 degrees N latitude and 71.0 degrees W longitude with warning actions:

N = geoidheight( 42.4, -71.0 )

Calculate the EGM2008 geoid height at two different locations with error actions.

N = geoidheight( [39.3, 33.4], [77.2, 36.5], 'egm2008', ...
'error')

Calculate a custom geoid height at two different locations with no actions.

N = geoidheight( [39.3, 33.4], [-77.2, 36.5], 'custom', ...
'geoidegm96grid','none')

References

Vallado, D. A. "Fundamentals of Astrodynamics and Applications." McGraw-Hill, New York, 1997.

NIMA TR8350.2: "Department of Defense World Geodetic System 1984, Its Definition and Relationship with Local Geodetic Systems."

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