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# eqa2grn

Convert from equal area to Greenwich coordinates

## Syntax

```[lat,lon] = eqa2grn(x,y) [lat,lon] = eqa2grn(x,y,origin) [lat,lon] = eqa2grn(x,y,origin,ellipsoid) [lat,lon] = eqa2grn(x,y,origin,units) mat = eqa2grn(x,y,origin...) ```

## Description

`[lat,lon] = eqa2grn(x,y)` converts the equal-area coordinate points `x` and `y` to the Greenwich (standard geographic) coordinates `lat` and `lon`.

`[lat,lon] = eqa2grn(x,y,origin)` specifies the location in the Greenwich system of the x-y origin (0,0). The two-element vector `origin` must be of the form `[latitude longitude]`. The default places the origin at the Greenwich coordinates (0º,0º).

`[lat,lon] = eqa2grn(x,y,origin,ellipsoid) ` specifies the ellipsoidal model of the figure of the Earth using `ellipsoid`. `ellipsoid` is a `referenceSphere`, `referenceEllipsoid`, or `oblateSpheroid` object, or a vector of the form ```[semimajor_axis eccentricity]```. The `ellipsoid` is a unit sphere by default.

`[lat,lon] = eqa2grn(x,y,origin,units)` specifies the units for the outputs, where `units` is any valid angle units value. The default value is `'degrees'`.

`mat = eqa2grn(x,y,origin...)` packs the outputs into a single variable.

This function converts data from equal-area x-y coordinates to geographic (latitude-longitude) coordinates. The opposite conversion can be performed with `grn2eqa`.

## Examples

```[lat,lon] = eqa2grn(.5,.5) lat = 30.0000 lon = 28.6479 ```

## Version History

Introduced before R2006a