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foldable map of Ida
Guest_jumpjack_*
post Nov 10 2008, 06:52 PM
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QUOTE (Tayfun Íner @ Nov 10 2008, 05:13 PM) *
Chuck the comparison photo is really impressive.

Due to Ida's irregular shape slices will not be contiguous and I suggest first we try it with Phobos. I will post the slices in DXF and CDR formats in a few days.

How do you make the slices? By hand?
Don't know if I have a suitable freeware SW to read DXF or CDR, would it be possible to export to the old WMF/EMF format?

Where can I download an asetrodi model in 3ds format? (or any other compatible with Google Sketchup)

Ok, questions are finished. rolleyes.gif
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chuckclark
post Nov 10 2008, 08:42 PM
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Thanks, Tayfun. Like I say, the view from the other direction is not so perfect -- I have an Adkins digital pic of that side, can you send me a digital image of the shape model from the same view? I'll make another comparison plate. Here, I'll post what I have . . .

Due to Ida's irregular shape slices will not be contiguous and I suggest first we try it with Phobos. I will post the slices in DXF and CDR formats in a few days.
[/quote] I agree. Especially as Ida is the most complex shape, best to work up to it.
Have you tried to assemble the Phobos map-model yet? Phobos model hold their shape fairly well without an infill, but they'll be much stronger with it.
Note that the slices will have to be truncated, primarily at the "blunt" end, where the map precis (the choice of boundary tree) leaves the largest lobe, or flattened facet. We'll probably have to work this out ad hoc, by trial and error. At the DPS meeting, some education experts were excited about the possibilities -- tactile, hands-on activity, etc. -- but immediately asked about some kind of solid fill. So I think it's worth the effort. We have stuff here called foam-core board; I'll probably use that to cut the slices. It comes in 1/8 inch thickness increments.
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t_oner
post Nov 10 2008, 08:43 PM
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By hand I presume you mean manually, no I will make them automatically.

I can probably convert them to WMF but DXF or CDR are more suitable if you are planning to cut them by laser.

You can download the models from the PDS Small Bodies Node. Celestia keeps some of them in a more friendly 3DS format.
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chuckclark
post Nov 10 2008, 08:46 PM
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this may surprise you but I don't have much familiarity with those programs. DXF is the only acronym I recognize, and VectorWorks is the cad system i use for architectural drawing.
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t_oner
post Nov 11 2008, 05:20 PM
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Here is a rendering from a similar angle.
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t_oner
post Nov 11 2008, 06:00 PM
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Here are the Phobos slices. As I don't know how they will be used, I left them in 3D space. They are 0.3 km's apart.
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chuckclark
post Nov 11 2008, 08:14 PM
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Well, so far so good. I downloaded and unzipped the file, then imported it into VectorWorks, where it appears to be all there.
I can probably figure out how to core an alignment hole or two through them, but I'm not sure I have the strength to print out each layer (must be thirty or so, right) on stock (how thick)?
Maybe someone else has a laser cutter?
Let me sleep on this. Maybe I'll think of something . . .

Great shot, by the way, Tayfun of the Northerly view of Ida. I'll work up a plate on that while I ponder this slices business.
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chuckclark
post Nov 15 2008, 06:54 PM
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QUOTE (Tayfun Íner @ Nov 11 2008, 01:00 PM) *
Here are the Phobos slices. As I don't know how they will be used, I left them in 3D space. They are 0.3 km's apart.

Well, here's what I think: cutting all those slices out of something looks like a real pain in the old asteroid, so to speak; and even if I had a laser cutter and matched sheet thickness to the appropriate scale, I'm sure I have the technical wherewithal to glue them all together evenly.
Surely that's not how you made (I'll stick with Ida as topic, but same applies to Phobos) this model, right? However this got made is the way to go, for good solid 3D models.
Even the original Eros models (the NEAR team had) used the assembled-slice method only to make a master object, then it was in turn used to make a mold, from which the production run was cast.

And yet all these methods leave us wanting the photomosaic imagery in real space, not just in the computer where we can't get our hands on it. Whence the advantage of foldable constant-scale natural boundary maps, with the disadvantage they're so easy to dent, if not crush.
So see next post for the rest of what I've come up with.
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chuckclark
post Nov 15 2008, 07:17 PM
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Okay, so borrowing a little from both systems, here is the csnb map of Ida along with a set of three (only three!) interlocking ribs, one rib for each major axis. The ribs' white lines indicate where slots are to be cut, black lines to remain as assembling guides. (Note that the short rib will go in as two separate pieces.)
DON'T, anyone, at the risk of extreme frustration!, take this plate for anything but a suggestion. I made the rib shapes from Tayfun's ORTHO VIEWS plate, and Ida is so extremely concave that the "short vertical rib" is only a guess for accurate, because its perfect shape is hidden from both directions. It needs some uncertain amount of trimming near point z. Plus, I haven't tried assembling this yet to see if in fact I've got the ribs and the map at the same scale.
BUT, with this as a guide, Tayfun will be able to generate these three ribs easily and accurately; and thickness of slice won't be an issue.

Just to lessen confusion, the ribs shown in Ortho Views are flipped from what is shown in the map plate.

Tayfun, if you'll make them for our asteroid set so far (Eros Ida, Phobos, Deimos), I'll set each in scale with the csnb maps, and trim them in where the folded csnb-form deviates from true shape. (Eros in particular is the troublesome one to hold up shape in hollow folded paper, and probably will need another "short" rib, parallel to the main short rib and centered on shoemaker.)

The assembled result will still be a bit susceptible to dents, but the overall skills required won't be at the level of a professional model builder to get it done.
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t_oner
post Nov 15 2008, 07:58 PM
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Chuck, that is brilliant. Here are your cuts both in vectoral and bitmap form.
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djellison
post Nov 15 2008, 09:26 PM
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GENIUS
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chuckclark
post Nov 17 2008, 02:01 PM
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QUOTE (djellison @ Nov 15 2008, 04:26 PM) *
GENIUS

Well, assuming you mean the ability to look at problems from outside the usual box, I plead guilty, and cravenly point the blame at having when back in grammar school specialized in play.

Or perhaps you mean the lucky magic that constant-scale natural boundary maps fold to replicate their originating object. I trace that idea to Albrecht Durer c1519, although that's a coincidental trace I owe entirely to the insights of the art historian Erwin Panofsky and his pal Marston Morse. I didn't uncover that connection to Durer's "prototopological" mappings until well into this project. Tell the truth, I had the good fortune as a first-grader to be challenged to "fix the problem with all these world maps"; problem being, "they're all stretchy at the edges."

And as for genius, I think it goes in greater measure to the slow-witted, like me. It took a good nine years of making these maps before it dawned on me that their essential characteristic is to rigorously put "constant-scale" (the equator on a Mercator or simple cylindrical map) at the edge -- edge no more stretchy, just what my challenger asked for! The "natural boundary" requirement is merely gravy, ensuring that the map's various and sundry lobes are composed of districts that make sense -- in this case valleys (aka basins or dales) -- rather than and abstract (pragmatic . . . objective) triangles or gores.

The general trick, seems to me, is to be able without prejudice to name something new. (For more info, see M. Faraday's confessions on his discovery of electromotive force.)

Here is the foldable Ida with the Tayfun-corrected ribs:
I haven't yet had time to try putting it together, so the caveat still holds about the ribs need shaving where the folded object differs from Ida's true shape. Also the caveat that I may have failed to maintain constant-scale at map edge, probably near point "n."
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Phil Stooke
post Nov 17 2008, 04:10 PM
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Very interesting and entertaining stuff. I think Chuck's approach opens up possibilities for all sorts of outreach and educational opportunities, built around 'make your own asteroid' kits for school or hobby uses.

Phil


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... because the Solar System ain't gonna map itself.
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t_oner
post Nov 21 2008, 06:59 PM
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Here are ribs for Eros.
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chuckclark
post Nov 21 2008, 10:02 PM
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QUOTE (Tayfun Íner @ Nov 21 2008, 01:59 PM) *
Here are ribs for Eros.

Wonderful, Tayfun, and I know you are busy at the moment, but would you have time to add an extra short rib (parallel to the "main" short rib) at the quarterpoint to the left (as we look at your image) of the main short rib? Reference lines for this new short rib on the two long ribs will be helpful too.
Hope that's not too much to ask. Having assembled several of the maps, I think this extra rib will be a great help in getting the Shoemaker region to hold its shape.
Thanks
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