'Location in global frame (a :py:class:`LocationGlobal`).
The latitude and longitude are relative to the
`WGS84 coordinate system <http://en.wikipedia.org/wiki/World_Geodetic_System>`_.
The altitude is relative to mean sea-level (MSL).
This is accessed through the :py:attr:`Vehicle.location` attribute:
.. code-block:: python
print "Global Location: %s" % vehicle.location.global_frame
print "Sea level altitude is: %s" % vehicle.location.global_frame.alt
Its ``lat`` and ``lon`` attributes are populated shortly after GPS becomes available.
The ``alt`` can take several seconds longer to populate (from the barometer).
Listeners are not notified of changes to this attribute until it has fully populated.
To watch for changes you can use :py:func:`Vehicle.on_attribute` decorator or
:py:func:`add_attribute_listener` (decorator approach shown below):
.. code-block:: python
@vehicle.on_attribute(\'location.global_frame\')
def listener(self, attr_name, value):
print " Global: %s" % value
#Alternatively, use decorator: ``@vehicle.location.on_attribute(\'global_frame\')``.'

@property
def global_frame(self):

    return LocationGlobal(self._lat, self._lon, self._alt)
