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Radar And Mariner 10, Best possible mapping, pre-Messenger
t_oner
post Dec 9 2006, 06:37 PM
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While reading this thread I realized I made the cylindrical map at http://www.lpl.arizona.edu/~rhill/alpo/mer...f/messenger.pdf, so here is my version of Phil's map.
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dvandorn
post Dec 9 2006, 08:10 PM
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Mucho, mucho gracias for the maps, Phil and Tayfun. To borrow a phrase... fascinating!

-the other Doug


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Phil Stooke
post Apr 8 2007, 06:18 PM
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I have updated my composite map of Mercury, adding a few extra bits from remaining radar images from the paper cited earlier. Wherever possible I have merged at least two overlapping images with different radar equators to reduce the north-south ambiguity. This is probably as good as it's going to get before Messenger arrives, unless new radar images suddenly appear.

Phil

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This is the northern hemisphere:

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Phil


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Phil Stooke
post Apr 8 2007, 06:19 PM
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... and the southern hemisphere:

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Phil


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volcanopele
post Apr 8 2007, 07:34 PM
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Using the above map, I ran through the first MESSENGER flyby in Celestia:

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ugordan
post Apr 8 2007, 07:48 PM
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Nice view VP. One thing I always wondered about visualization programs like Celestia is what kind of map projections they assume as textures. I always thought cylindric texture maps were required, but the vertical spacing of latitude lines in your view seems to be shrinking at the poles. Is this normal or is it suggesting a spherical projection maybe?

EDIT: On second thought, latitude lines shrinking is logical when properly mapped. I'd also expect cylindrical maps to behave the same so my non-extitent expertise in maps leads me to believe Phil's map is not cylindric, correct?


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Phil Stooke
post Apr 8 2007, 08:30 PM
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That is really cool, VP, thanks.

ugordan, I think you're just seeing the foreshortening one would expect near the limbs, north and south. My map was simple cylindrical, equal spacing of meridians and parallels. THere are other clindrical projections - Mercator, where spacing increases towards the poles to preserve conformality (shape), and perspective cylindrical where they get close towards the poles to preserve area.

Every planetary scientist should take a course in map projections!

Phil


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ugordan
post Apr 8 2007, 08:39 PM
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I see, Phil. I was under the impression that in 3D graphics, by "cylindrical" that which you describe as perspective cylindrical is implied, whereas in "spherical" map your simple cylindrical map was assumed.

I never could figure out the terminology. Then again, I don't call myself a planetary scientist so you'll have to forgive me. wink.gif


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Phil Stooke
post Apr 9 2007, 03:16 AM
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I don't mean you! But I encounter so many scientists who use maps all the time and don't understand them at all... Some terrible things are done in the name of cartography, even in the best journals. Perhaps the most common is referring to any cylindrical projection as Mercator.

Phil


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lyford
post Apr 9 2007, 03:51 PM
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QUOTE (Phil Stooke @ Apr 8 2007, 08:16 PM) *
Some terrible things are done in the name of cartography

Would this be the cynical projection? laugh.gif

One of the things I truly love about this forum (among many others) is how much I learn and how much threads like this inspire me to educate myself even more. I stole my one of my wife's GIS manuals for a little light night reading and what do you know, it's online as well:

ESRI's Understanding Map Projections (2 MB PDF file)

Beginner level, but I found it helpful.... I trust that the system works for Mars as well as Earth, though Eros, Itokawa et al might require different coordinate systems? Phil?

This page has a good set of references for the cartographically challenged:

Harvard GIS Resources

And of course, what enthusiast autodidact post would be complete without mentioning the golden oldies:

Remote Sensing Tutorial

and

JPL's Basics of Spaceflight


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"Zis is not nuts, zis is super-nuts!" Mathematician Richard Courant on viewing an Orion test
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tedstryk
post Apr 9 2007, 07:02 PM
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All this is well and good, Phil, but let me ask you a more sophisticated question. When you get a map out, whether it be cylindrical, mercator, or whatever, can you fold it back up properly? biggrin.gif


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Phil Stooke
post Apr 9 2007, 07:27 PM
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Yes, Ted, I use them to make cootie-catchers... or like this:

http://www.ssc.uwo.ca/geography/spacemap/psg.jpg

and

http://www.ssc.uwo.ca/geography/spacemap/png.jpg

which really do fold up!

Phil


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JRehling
post Apr 9 2007, 08:34 PM
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[...]
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PhilHorzempa
post Apr 10 2007, 06:05 PM
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The significance of all of this effort to squeeze out interpretations of Mercury's
surface from fuzzy Radar or Earth-based telescopes lies in our future efforts
to image Extra-Solar Terrestrial Planets. When the Planet Imager flies (someday)
after TPF, the images of those worlds will be astonishing, but they will still be only
fuzzy views, much as we see Mercury today from Earth-based telescopes.
However, by then, we will have had additional experience in interpreting those
images because of this present effort. It will be very revealing to see what
Messenger tells us, within a few months, about these present estimates of
what Mercury's "Far Side" will look like.

Another Phil
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Phil Stooke
post Apr 10 2007, 06:09 PM
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I will go on record saying that I don't believe in Skinakas.

Phil


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