Reprojection works better than it has any right to

[fivemack]

Y'know, if testing an algorithm which turns out to rely absolutely critically on precise to-the-pixel identification of surface features between images, maybe I should have chosen something other than Titan, an object all of whose surface features have critically fuzzy edges.

To obtain this image (click on it! it grows bigger!), I took the four photos that I photo-mosaiced incompetently yesterday, then solved for the best-fit circle to the ones showing limbs, then solved for the circle parameters for the ones not showing limbs by requiring the features to map to the same places as features whose positions I knew by reference to the limbs. I've then cropped off the bits that were black, or so close to a pole as to be absurdly fuzzy. I'm impressed at the continuity of scale and of colour.

The scale on this map is slightly too small to see the Mysterious Scratch without the eye of faith, but it's visible at the terminator on the big image.



This is a cylindrical projection, nothing like as good even as Mercator's, and with arbitrarily chosen equator and poles.

It is an odd feeling to be producing what I think may be the first maps of unexplored parts of a new world. I wonder if anyone will bother to name these craters. There are enough hundreds of them to drain the name-stocks of the Aeneid many times over.

Comments

[shimgray.livejournal.com]

The Mysterious Scratch is interesting; rift of some form? It does seem to be fairly recent - it overlays all but one of the features it passes through, I think. (But it's hard to say)

There's a couple of sharp linear features on the Moon that might be useful comparisons, but none that directly map as far as I can recall.

(also: um. hi. saw the pretty pictures on your comments to a post of James', and wandered over...)

[fivemack.livejournal.com]

The Mysterious Scratch is on the order of twice as long as the Straight Wall on the Moon, and significantly straighter.

http://legault.club.fr/alpinevalley_w.jpg and http://legault.club.fr/mur_m.jpg look like the same sort of thing, but the surroundings on Luna are clearly mariae, which Dione doesn't seem to have.

Glad someone likes the pictures. I should probably have gone to bed some hours ago.

[shimgray.livejournal.com]

There's also other rift features running at an angle to this, on the upper right-hand side. Not sure what that might indicate, except that they're "rougher", which gives the impression that those are more likely to be real / there's multiple processes at work.

A friend suggested ice-cracking? Apparently there's analogies on Ganymede, but I haven't chased that up.