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From: Xilo Musimene
Subject: Earth heightfield, colormaps, etc...
Date: 13 Apr 2003 19:31:15
Message: <3E9965F1.3030804@hotpop.com>
Hi,
   I'm looking for some very high quality pictures of the earth, 
specially europe.  I would need the land heightfield and the land colormap.

If anyone can help me, i'd greatly appreciate!

Thanks,
   Xilo


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From: Marc Jacquier
Subject: Re: Earth heightfield, colormaps, etc...
Date: 14 Apr 2003 03:47:06
Message: <3e9a677a$1@news.povray.org>
here
http://earthobservatory.nasa.gov/Newsroom/BlueMarble/BlueMarble.html
and here for height_field
http://gw.marketingden.com/planets/earth.html

Marc


3E9### [at] hotpopcom...
> Hi,
>    I'm looking for some very high quality pictures of the earth,
> specially europe.  I would need the land heightfield and the land
colormap.
>
> If anyone can help me, i'd greatly appreciate!
>
> Thanks,
>    Xilo
>


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From: Xilo Musimene
Subject: Re: Earth heightfield, colormaps, etc...
Date: 14 Apr 2003 10:26:15
Message: <3E9A37B8.2050302@hotpop.com>
> here
> http://earthobservatory.nasa.gov/Newsroom/BlueMarble/BlueMarble.html

This website is awesome, with quality images beyond what I expected!

> and here for height_field
> http://gw.marketingden.com/planets/earth.html

Though, this one offers less quality, I'd have to pay to download better 
heightfields.
   Since I'm specially interested in europe, I'd have to have a much 
better height field than that in order to make interesting landscape... 
  Though it'll be perfect for a start!


Thanks a lot Marc!
   Xilo


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From: Remco de Korte
Subject: Re: Earth heightfield, colormaps, etc...
Date: 14 Apr 2003 14:18:53
Message: <3E9AFB79.A3A55428@onwijs.com>
Xilo Musimene wrote:
> 
> > here
> > http://earthobservatory.nasa.gov/Newsroom/BlueMarble/BlueMarble.html
> 
> This website is awesome, with quality images beyond what I expected!
> 
> > and here for height_field
> > http://gw.marketingden.com/planets/earth.html
> 
> Though, this one offers less quality, I'd have to pay to download better
> heightfields.
>    Since I'm specially interested in europe, I'd have to have a much
> better height field than that in order to make interesting landscape...
>   Though it'll be perfect for a start!
> 
> Thanks a lot Marc!
>    Xilo

I can perhaps give you a heightfield with a higher resolution, but the
vertical resolution might not be that good (bitmap with range [0..255]).
I got the USGS data here: 
http://edcdaac.usgs.gov/gtopo30/
It's a 5400x4800 pixel bitmap for the Europe part (lots of sea and
ocean).

Oh, just checked, I only have North West Europe right now. The other
parts should be on the site as well.

Remco


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From: Xilo Musimene
Subject: Re: Earth heightfield, colormaps, etc...
Date: 14 Apr 2003 21:28:43
Message: <3E9AD300.7060604@hotpop.com>
> I can perhaps give you a heightfield with a higher resolution, but the
> vertical resolution might not be that good (bitmap with range [0..255]).
> I got the USGS data here: 
> http://edcdaac.usgs.gov/gtopo30/
> It's a 5400x4800 pixel bitmap for the Europe part (lots of sea and
> ocean).
> 
> Oh, just checked, I only have North West Europe right now. The other
> parts should be on the site as well.

Well, I've seen those images, at the site you mentionned, and those are 
not heightfields, but rather rendered heightfield...  can you make a 
real heightfield out of it?   Even if the scale has only 256 values, it 
would be perfect for my use!

If possible, and I don't want to ask for too much, I'd like to have the 
four quadrants concerning europe...  but only if it's possible for you, 
or if you can explain to me how to read USGS data I could possibly write 
a program to make images out of it...  I'm a programmer...

Thanks a lot,
   Xilo


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From: Remco de Korte
Subject: Re: Earth heightfield, colormaps, etc...
Date: 14 Apr 2003 21:49:28
Message: <3E9B6516.24AFD32C@onwijs.com>
Xilo Musimene wrote:
> 
> 
> If possible, and I don't want to ask for too much, I'd like to have the
> four quadrants concerning europe...  but only if it's possible for you,
> or if you can explain to me how to read USGS data I could possibly write
> a program to make images out of it...  I'm a programmer...
> 
> Thanks a lot,
>    Xilo

Well, that's what I did. The format is very straightforward. If you
download the four sectiosn, each section has several files, but you'll
only need the DEM file. It has the height data stored in 5400 rows and
4800 colums, with 2 bytes for each pixel. Couldn't be simpler (also
couldn't be more bloated...).
If you have the four sections you can combine them to one fairly huge
heightfield - or at least cut out the part you need.

Remco


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From: Xilo Musimene
Subject: Re: Earth heightfield, colormaps, etc...
Date: 14 Apr 2003 23:09:44
Message: <3E9AEAAD.8080400@hotpop.com>
> Well, that's what I did. The format is very straightforward. If you
> download the four sectiosn, each section has several files, but you'll
> only need the DEM file. It has the height data stored in 5400 rows and
> 4800 colums, with 2 bytes for each pixel. Couldn't be simpler (also
> couldn't be more bloated...).
> If you have the four sections you can combine them to one fairly huge
> heightfield - or at least cut out the part you need.

Good, I should get started right away!  Do you think the seperation can 
be seen or is the data perfectly cut?

And is there any more data I could read like coloration? DEM would be 
elevation, I see there are many other files also do you know what they 
are for?

Thanks!
   Xilo


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From: Remco de Korte
Subject: Re: Earth heightfield, colormaps, etc...
Date: 15 Apr 2003 09:45:42
Message: <3E9C0CEF.8CA07A87@onwijs.com>
Xilo Musimene wrote:
> 
> > Well, that's what I did. The format is very straightforward. If you
> > download the four sectiosn, each section has several files, but you'll
> > only need the DEM file. It has the height data stored in 5400 rows and
> > 4800 colums, with 2 bytes for each pixel. Couldn't be simpler (also
> > couldn't be more bloated...).
> > If you have the four sections you can combine them to one fairly huge
> > heightfield - or at least cut out the part you need.
> 
> Good, I should get started right away!  Do you think the seperation can
> be seen or is the data perfectly cut?
> 
> And is there any more data I could read like coloration? DEM would be
> elevation, I see there are many other files also do you know what they
> are for?
> 
> Thanks!
>    Xilo

My guess is the sections will fit perfectly since these seem to be
cutouts from a huge database.
I have a documentation of the file formats I can send you. I think it
came from the same site I found the data so you could also check there. 
These are the included files:

   DEM        digital elevation model data
   HDR        header file for DEM
   DMW        world file
   STX        statistics file
   PRJ        projection information file
   GIF        shaded relief image
   SRC        source map
   SCH        header file for source map
I don't see any colour information, the GIF is just a representation of
the data in the DEM file.
The SRC-file funnily enough contains the source for the data for every
pixel. I don't see how that can help...

Cheers!

Remco


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From: Xilo Musimene
Subject: Re: Earth heightfield, colormaps, etc...
Date: 15 Apr 2003 18:04:20
Message: <3E9BF499.9010803@hotpop.com>
> I don't see any colour information, the GIF is just a representation of
> the data in the DEM file.
> The SRC-file funnily enough contains the source for the data for every
> pixel. I don't see how that can help...

Ok good!  I already have an image anyway, I'll just pray it fits 
perfectly! If not, I'll have to retouch it...

I'll check the source website thoroughly, thanks a lot Remco!

Xilo


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From: Xilo Musimene
Subject: Re: Earth heightfield, colormaps, etc...
Date: 15 Apr 2003 21:56:41
Message: <3E9C2B0E.6000606@hotpop.com>
> I don't see any colour information, the GIF is just a representation of
> the data in the DEM file.
> The SRC-file funnily enough contains the source for the data for every
> pixel. I don't see how that can help...

Ok, I've been working on my program a lot and it now works... it 
currently outputs a bmp and the grayscale is scaled to 8bits, 
unfortunately...  I'll work with that for now and eventually, I will 
write Grayscale 16bit PNGs!

Though, there is something extremely strange about the image I get... 
First, I realized the countrys near Holland, etc, were "really" lower 
than sea level!  And second, holland is white, sea is gray, and land is 
black...  but in the alps, where the elevation is very high, it gets 
lighter...

I would have expected the land to be on the coast almost the same value 
as the sea, but there is a definite sharp change from light gray(sea) to 
dark gray(land), and that can be seen on all coasts...

I believe the sea has a special code, and should not be displayed like 
the land, I don't know...  I could send you a very small jpeg of some 
region of the result I get so you can see for yourself and this way 
maybe you'll understand what's happenning?

Thanks,
   Xilo


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