ObsAltObsAlt - The geodetic altitude of the observer

Description:
This attribute specifies the geodetic altitude of the observer, in metres, relative to the IAU 1976 reference ellipsoid. The basic FrameFrame class makes no use of this attribute, but specialised subclasses of Frame may use it. For instance, the SpecFrameSpecFrame, SkyFrameSkyFrame and TimeFrameTimeFrame classes use it. The default value is zero.
Type:
String.
Class Applicability:
Frame
All Frames have this attribute.
SpecFrame
Together with the ObsLonObsLon, EpochEpoch, RefRARefRA and RefDecRefDec attributes, it defines the Doppler shift introduced by the observers diurnal motion around the earths axis, which is needed when converting to or from the topocentric standard of rest. The maximum velocity error which can be caused by an incorrect value is 0.5 km/s. The default value for the attribute is zero.
TimeFrame
Together with the ObsLon attribute, it is used when converting between certain time scales (TDB, TCB, LMST, LAST)