The function converts the position of B (typically body) relative to E (typically Earth),
the n-vector `n_EB_E`

to cartesian position vector ("ECEF-vector"), `p_EB_E`

,
in meters.

## Arguments

- n_EB_E
n-vector of position B, decomposed in E (3x1 vector) (no unit)

- z_EB
Depth of system B, relative to the ellipsoid (z_EB = -height) (m, default 0)

- a
Semi-major axis of the Earth ellipsoid (m, default [WGS-84] 6378137)

- f
Flattening of the Earth ellipsoid (no unit, default [WGS-84] 1/298.257223563)

## Details

The calculation is exact, taking the ellipticity of the Earth into account.

It is also nonsingular as both n-vector and p-vector are nonsingular
(except for the center of the Earth).
The default ellipsoid model used is WGS-84, but other ellipsoids (or spheres) might be specified
via the optional parameters `a`

and `f`

.

## References

Kenneth Gade A Nonsingular Horizontal Position Representation.
*The Journal of Navigation*, Volume 63, Issue 03, pp 395-417, July 2010.

## Examples

```
n_EB_E <- lat_lon2n_E(rad(1), rad(2))
n_EB_E2p_EB_E(n_EB_E)
#> [1] 6373287.3 222560.1 110568.8
```