I'm a bit confused by the image and its caption. Any clarification of what I'm seeing and reading would be appreciated. I am thinking that the portion of the image which I've excerpted here is the Verona Rupes cliff, and the arrow indicates an approximate trajectory for a thrill-seeker trying a cliff-dive. Is this correct?
Yes, that view perspective is correct
Meanwhile, the other references I've followed seem to indicate that this cliff, conjectured to have been created by fault movement, is at least 5 km tall, perhaps 10 km, but not 20km. The other Wikipedia materials I found in the references indicate that some canyon on Miranda (perhaps this same canyon), is 20 km deep, but not that there is any 20 km high cliff, as the APOD caption seems to indicate. Then again, how to reconcile those statements. If the cliff is only 5-10 km, where on Miranda is there a depth of 20 km ?
Yeah, there's some conflicting statements between wiki and the APOD. Even after looking up the Voyager NAC Camera Details
and analyzing the and "original" image PIA00044
, the numbers don't work out. (I estimated a minimum fault height ~3x larger!) It wasn't until I used basic measurable data: Miranda diameter coupled with a 20-plus km crater measurement in PIA18185
, then using that crater size to compare the scarp in PIA01354
did I agree with the APOD description of ~20km cliff height.
And how do astronomers come to those figures? Was it done strictly from visual images, or was there some other data, such as radar data that help figure out such things?
Basically the same way I did - Voyager had no ranging instruments to get relative elevations. Additional projection corrections could be done, but the 20-km estimate looks sound to me.