This function is used (for instance) when projecting voxel model locations where the user expects that the vertical position will not change. The regular ConvertXYZ_PJ may result in shifts of hundreds, even a thousand meters in case where you are going from the geoid to an ellipsoid. The value of Z can have an important effect on the accuracy of the results, as the normal ConvertXY_PJ assumes a value of Z=0 internally and calls ConvertXYZ_PJ.

public void ConvertXYFromXYZ(
	ref double x,
	ref double y,
	double z
)

Public Sub ConvertXYFromXYZ ( 
	ByRef x As Double,
	ByRef y As Double,
	z As Double
)

public:
void ConvertXYFromXYZ(
	double% x, 
	double% y, 
	double z
)

member ConvertXYFromXYZ : 
        x : float byref * 
        y : float byref * 
        z : float -> unit