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Qeustion: How to convert ETOPO1 to greyscale?

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#1
jelle

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Hello everyone,

I've been trying software and waiting for maps to download and i can't come to the end result i want so that's why i'm making this topic.

I want to use the ETOPO1 format ice-surface map from http://www.ngdc.noaa...bal/global.html as a greyscale heightmap. I have downloaded and tried GEODAS and was able to get a blue shade map of the world but i can't export it as an image in it screencapture won't work because the map is a way bigger resolution as my screen supports. And scaling it up afterwards would get quircky.

An other solution would be to somehow merge the heightmap and bathymetric map from http://earthobservat...e_monthlies.php but the color shades would mix up i guess, but if it's possible i'm open to it. I don't expect it is but just to be sure.

So yeah, i basiclly am looking for a heightmap (as an image file, TIF?) of both under and above water terrain, with the ice cap on top of it for the poles in a size of atleast 21600*10800. I'm OK with downscaling. I'm willing to install freeware or trial software whatever. I'm just seriously annoyed at this point i couldn't figure it out after 6 hours of googling and trying stuff out that i have to bother you with the question.

I'm basicly looking for a heightmap of the world, above and below water, with icecaps on a scale of 21600*10800 pixels or higher (rougly 1:2000 if im right). I think the best bet is to change the colors of the ETOPO1 scheme to shades of a same color -preferably direction to greyscale-. All suggestions are appreciated.

Kind regards,

Jelle

#2
frax

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If you just want a gray-scale height map (how many bits? real values or stretched?) you should be able to do a custom request on the ETOPO1 website and download it as binary or ArcInfo ASCII raster. That is a common format that should open in GIS Software, like the free FWTools or Quantum GIS (QGis) - you can google to find the links to those. Maybe the binary export exports even open in Photoshop. A very good and fast inexpensive option is GlobalMapper.

That would give you a height map - but if you want glaciers separated it gets a bit more complicated. ETOPO1 has the top of glaciers and ice sheets in the elevation data. Not sure what the best way forward would be - you would have to integrate data from a different source which would smack up the level of complexity quite a bit.

An easy to use option, which might also be better looking is CleanTOPO2. I think it has edits and imperfections fixed. As I understand it ETOPO1 is also just upscaled in large areas for e.g. bathymetry, so it does not necessary contain more detail. CleanTOPO2 is available for download as 16-bit TIFFs, which should open fine in e.g. Photoshop (knock on wood). It is only half of your suggested resolution though...
http://www.shadedrel...leantopo2/#data
Hugo Ahlenius
Nordpil - custom maps and GIS
http://nordpil.com/
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