I've been looking but I keep finding contradictory answers.
Order of Kilopi
I've been looking but I keep finding contradictory answers.
"Occam" is the name of the alien race that will enslave us all eventually. And they've got razors for hands. I don't know if that's true but it seems like the simplest answer."
Stephen Colbert.
Order of Kilopi
I don't know about the others, but the zero datum for Mars has certainly evolved. It was originally set to the height with a mean atmospheric pressure of 6.1 mbars during the Mariner missions. But MOLA has since since moved away from that very labile standard to use an equipotential surface derived from gravity data, with a mean equatorial radius of 3,396,000 metres.
Grant Hutchison
Order of Kilopi
So both MESSENGER at Mercury and Magellan at Venus seem to have used a reference radius for topographic mapping. The MESSENGER global topo map was referenced to 2439400m radius;Magellan to 6051000m. But these are essentially free choices for convenience--the real reference point is the centre of the planet, so I wouldn't be surprised if different mappers made different choices.
Grant Hutchison
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