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# geocradius

Estimate radius of ellipsoid planet at geocentric latitude

## Syntax

r = geocradius(lambda)
r = geocradius(lambda, model)
r = geocradius(lambda, f, Re)

## Description

r = geocradius(lambda) estimates the radius, r, of an ellipsoid planet at a particular geocentric latitude, lambda. lambda is in degrees. r is in meters. The default ellipsoid planet is WGS84.

r = geocradius(lambda, model) is an alternate method for estimating the radius for a specific ellipsoid planet. Currently only 'WGS84' is supported for model.

r = geocradius(lambda, f, Re) is another alternate method for estimating the radius for a custom ellipsoid planet defined by flattening, f, and the equatorial radius, Re, in meters.

## Examples

Determine radius at 45 degrees latitude:

```r = geocradius(45)

r =

6.3674e+006```

Determine radius at multiple latitudes:

```r = geocradius([0 45 90])

r =

1.0e+006 *

6.3781    6.3674    6.3568```

Determine radius at multiple latitudes, specifying WGS84 ellipsoid model:

```r = geocradius([0 45 90], 'WGS84')

r =

1.0e+006 *

6.3781    6.3674    6.3568```

Determine radius at multiple latitudes, specifying custom ellipsoid model:

```f = 1/196.877360;
Re = 3397000;
r = geocradius([0 45 90], f, Re)

r =

1.0e+006 *

3.3970    3.3883    3.3797```

## References

Stevens, B. L., and F. L. Lewis, Aircraft Control and Simulation, John Wiley & Sons, New York, NY, 1992

Zipfel, P. H., and D. E. Penny, Modeling and Simulation of Aerospace Vehicle Dynamics, AIAA Education Series, Reston, VA, 2000

## See Also

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