QUESTION:
How do you measure the height of various surface features on Mars?

ANSWER from Bruce Jakosky on November 24, 1997:
The variations in topography on Mars have been measured by using earth-based
radar measurements, by measuring the thickness of the atmosphere above a
given point, and, most recently, using laser altimetry from the Mars Global
Surveyor spacecraft.  The last technique is the most accurate and provides
the most-detailed information.  Also, by the end of the Mars Global Surveyor
mission, the laser altimetry will provide complete global coverage.  This is
something that has been lacking in the past.