Next: ObsLat - The geodetic latitude of the observer
Up: AST Attribute Descriptions
Previous: ObjSize - The in-memory size of the Object
ObsAlt
-
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 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:
- String.
- Class 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)
Next: ObsLat - The geodetic latitude of the observer
Up: AST Attribute Descriptions
Previous: ObjSize - The in-memory size of the Object
AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 211
R.F. Warren-Smith & D.S. Berry
24th May 2011
E-mail:ussc@star.rl.ac.uk
Copyright (C) 2009 Science \& Technology Facilities Council