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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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> 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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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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> 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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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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> 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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> 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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> 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...
Nevermind... I fixed it... after rereading again and again the
documentation, I found out that the sea area, has the value -9999 (no
data has been registered for the area)... since the lowest plance on
earth is at -400 meters I think. This give a value of -30, so I just
changed all -9999 to 0 and BINGO! I get a perfect heightfield of europe!
Though my program can only output a 8bit bmp... I'll work out a way to
write a Grayscale PNG of 16bit!
See ya!
Xilo
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Xilo Musimene wrote:
>
> > 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...
>
> Nevermind... I fixed it... after rereading again and again the
> documentation, I found out that the sea area, has the value -9999 (no
> data has been registered for the area)... since the lowest plance on
> earth is at -400 meters I think. This give a value of -30, so I just
> changed all -9999 to 0 and BINGO! I get a perfect heightfield of europe!
>
> Though my program can only output a 8bit bmp... I'll work out a way to
> write a Grayscale PNG of 16bit!
>
> See ya!
> Xilo
Great, that's what I had to figure out too. It's obvious once you know
it... :)
And yes, a great part of the Netherlands is below sea level. I'm sitting
in such a pit now.
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> Great, that's what I had to figure out too. It's obvious once you know
> it... :)
Yes, indeed... and it's pretty interesting to have on the same data the
difference between sea and land, so I can use it for a mask or
something like that...
> And yes, a great part of the Netherlands is below sea level. I'm sitting
> in such a pit now.
Hehe, I did know such thing, but I had to see it on a heightfield of the
planet to believe it! ;)
See ya,
Xilo
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