Documentation

Geoid Height

Calculate undulations/height

Library

Environment/Gravity

Description

The Geoid Height block calculates the geoid height using the Geopotential model parameter. The block interpolates the geoid heights from a grid of point values in the tide-free system. It uses the specified geopotential model to degree and order 360. The geoid undulations are relative to the WGS84 ellipsoid.

The interpolation scheme wraps over the poles to allow for geoid height calculations at and near these locations.

Parameters

Units

Specifies the parameter and output units:

Units

Height

Metric (MKS)

Meters

English

Feet

Geopotential model

From the list, select the geopotential model.

Geopotential ModelDescription
EGM96 (Earth)

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

EGM2008 (Earth)

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 block calculates geoid heights to an accuracy of 0.001 m for this model.

    Note:   This block requires that you download geoid data for the EGM2008 Geopotential Model with the Add-On Explorer. Click the Get data button to start the Add-On Explorer. For more information, see aeroDataPackage. If the data is installed, the Get data button does not appear.

Custom

Custom geopotential model that you define in Geopotential mat-file. This block calculates geoid heights to an accuracy of 0.01 m for custom models. Selecting Custom enables the Geopotential mat-file parameter.

Geopotential mat-file

Specifies the MAT-file the defines your custom geopotential model. Selecting Geopotential model > Custom enables this parameter.

Data type

Specifies the data type of the input and output signals. From the list, select double or single.

Action for out-of-range input

Defines action for out-of-range input. Specify one:

'Error'
'Warning' (default)
'None'

Inputs and Outputs

InputDimension TypeDescription

First

ScalarContains geocentric latitude in degrees, where north latitude is positive, and south latitude is negative. Input latitude must be of type single or double. If latitude is not in the range from –90 to 90, the block wraps it to be within the range.

Second

ScalarContains geocentric longitude in degrees, where east longitude is positive in the range from 0 to 360. Input longitude must be of type single or double. If longitude is not in the range from 0 to 360, the block wraps it to be within the range.

OutputDimension TypeDescription

N

ScalarContains the geoid height in selected length units. The data type is the same as the latitude in the first input.

Limitations

This block has the limitations of the selected geopotential model.

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."

National Geospatial-Intelligence Agency Web site: http://earth-info.nga.mil/GandG/publications/vertdatum.html

Introduced in R2010b

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