#### Description:

This attribute specifies the geodetic altitude of the observer, in metres, relative to the IAU 1976 reference ellipsoid. The basic Frame class makes no use of this attribute, but specialised subclasses of Frame may use it. For instance, the SpecFrame, SkyFrame and TimeFrame classes use it. The default value is zero.

Type:

  Floating point.

#### Applicability

##### Frame

All Frames have this attribute.

##### SpecFrame

Together with the ObsLon, Epoch, RefRA and RefDec 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)
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