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PostPosted: Thu, 06-03-08, 9:52 GMT 
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Frank Gregorio has asked me to collaborate on an educational project that shows the Yucatan asteroid impact 65 million years ago. The base of this will have to be to discover, and from that, create a texture map that shows the Earth as it looked like before the impact. That is the task i am setting forward to do here.

Now, first of all, we will have to define what resolution to create the map in. Frank wants a very high resolution, but that is impractical if one is to show an animation, and there is no point in going very close to an Earth that we cannot know what looked like in detail - anything closer than a general representation will necessarily be fiction, and so not usable in an educational setting anyway. However, to be really useful, the map should have print-quality resolution. So, a middle ground is called for:

A 4k map (4096x2048 pixels at 72 dpi) will give us a 300 dpi print quality at A4 (slightly higher and narrower than the american letter format). This is larger than the format of most books.

So, it makes sense to make it a 4k map. When this is to be used in an animated Celestia add-on, it will have to be at 1k or 2k anyway, to make for reasonable framerates.

However, it is entirely possible to build a Virtual Texture on top of the 4k map that shows greater detail for the impact area. By using the BMNG dataset, one can get at least up to 64k resolution of the Yukatan, if that is desirable, though i cannot imagine that high resolution to be necessary. More on that later.

For now, i will outline the project.

1. Documentation.
Before creating the map, we need to know as much as possible on what the Earth actually looked like 65 million years ago. Frank has sent me this map:
Image
... We will need solid documentation on how this information was achieved. The reason i ask this, is because even though this view might work well for an animation of the impact, t is not good enough for a map that can be used for other purposes (say, in a textbook on the subject); for this, we need to verify how sound the data is, where it comes from, who made it, etc...

If this map is our state-of-the-art knowledge of the 65MY Earth, i will use it as a base for our 4k map.

2. Building the map
I will base our map on the BMNG dataset, since it is both publicly available and the best quality maps out there today. It is available for all months of the years, so we will probably create a hybrid of several months to get as close to the ice coverage of 65MY as possible, and then modify coastlines, vegetation colors, etc. to match what info we have. But there will only be modifications to a pixel if we know something about it!

Here is the BMNG Earth, of a nothern winter month:
Image

As you can see, it is very different from the 65MY image above. However, it is our current reality (or last years, at least).
The first challenge, then, is to define *how* to change the BMNG map.

Frank, can we start with getting what info there is on the 65MY picture above?

- rthorvald


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PostPosted: Thu, 06-03-08, 13:23 GMT 
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Just my usual observation concerning this BMNG map... Where's the Arctic ice?
Sorry, but I just don't understand why people continue to use a map which is
obviously incomplete.

Thanks, Brain-Dead

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PostPosted: Thu, 06-03-08, 13:56 GMT 
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For incomplete, how so? It shows all the land masses. The ice is not a permanent thing, it is basically just weather.

But no worry, polar ice will be there where needed... :-)

- rthorvald


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PostPosted: Thu, 06-03-08, 14:51 GMT 
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Again Runar, this is just my personal opinion. If the ice is represented at the Antarctic end of the
world, then it should be shown at the Arctic end also should it not? Or, are you saying that the
Earth had NO Arctic ice caps at the time you're going to represent with this map?

Pay no attention to me here. It's just that this particular map bothers the hell out of me since
it is - again - obviously incomplete. <shrug>

Thanks, Brain-Dead

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PostPosted: Thu, 06-03-08, 15:16 GMT 
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BobHegwood wrote:
If the ice is represented at the Antarctic end of the world, then it should be shown at the Arctic end also should it not?

But Antarctica is not ice, it is land. Norway is just as white on that map, for the same reason Antarctica is.

I do not see the BMNG map as incomplete just because it does not show a lot of frozen water on top of liquid water.

As for our 65 million year old Earth map - it will have polar ice where there was polar ice, if there exists data on how this differ from the modern Earth.

- rthorvald


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PostPosted: Thu, 06-03-08, 17:41 GMT 
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rthorvald wrote:
But Antarctica is not ice, it is land. Norway is just as white on that map, for the same reason Antarctica is.

I do not see the BMNG map as incomplete just because it does not show a lot of frozen water on top of liquid water.
- rthorvald


Okay, I think I understand then. You're saying that there is NO land in the arctic circle?
Sorry, but - as usual - I simply did not know that. In fact, I knew that some land existed in the
Antarctic circle, but I really had no idea that the same thing does not occur at the North
Pole.

Now you know why I'm Brain-Dead... :oops:

Thanks, Bob


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PostPosted: Thu, 06-03-08, 19:23 GMT 
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BobHegwood wrote:
rthorvald wrote:
But Antarctica is not ice, it is land. Norway is just as white on that map, for the same reason Antarctica is.

I do not see the BMNG map as incomplete just because it does not show a lot of frozen water on top of liquid water.
- rthorvald


Okay, I think I understand then. You're saying that there is NO land in the arctic circle?
Sorry, but - as usual - I simply did not know that. In fact, I knew that some land existed in the
Antarctic circle, but I really had no idea that the same thing does not occur at the North
Pole.

Now you know why I'm Brain-Dead... :oops:

Thanks, Bob


Bob,

the old Blue Marble textures had a fairly low resolution actic ice layer as part of their distribution. For the reasons Runar mentioned already and due to lack of menpower --as the BMNG lead scientist Reto Stoeckli explained to me--, the BMNG data are NOT delivered with an arctic ice layer.

One may either copy the old Blue Marble one or live without arctic ice...

+++++++++++++++++++++++++++++++++++
Anyway, one thing is for sure: 65 million years ago the arctic ice layer was different from the BlueMarble one ;-)
+++++++++++++++++++++++++++++++++++

F.


Last edited by t00fri on Fri, 07-03-08, 0:39 GMT, edited 1 time in total.

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PostPosted: Thu, 06-03-08, 21:18 GMT 
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Besides....... :|

- rthorvald


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PostPosted: Fri, 07-03-08, 0:22 GMT 
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Again, thank you both for the explanation. I really did NOT understand this relationship
and shall forevermore remain educated to this fact - now that it has been explained to
me properly.

I honestly don't know why this didn't register at some point in the past though. You'd
think that I might have uncovered these facts at some time wouldn't you? Ah well,
as always you educate me, and I really appreciate the effort here.

Take care, Brain-Dead


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PostPosted: Wed, 23-12-09, 21:47 GMT 
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From what I've seen this is one of the best maps around that depicts this (and other earlier) time periods. ARC Sciences has made this into a proprietary movie for Science On A Sphere.

http://sos.noaa.gov/datasets/Land/paleo.html

References are here:

http://jan.ucc.nau.edu/~rcb7/globaltext2.html


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