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Altitude (and 3D) with ASTER GDEM (Tutorial)

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Altitude (and 3D) with ASTER GDEM (Tutorial) Empty Altitude (and 3D) with ASTER GDEM (Tutorial)

Post  yip Tue Oct 30, 2012 1:36 pm


The app orux recommends (High Altitude) keeps crashing on my device, so here is another way.

Moreover, AFAIK, the app provides only SRTM data, and contain ads, therefore less trustable .
AFAIK, SRTM is limited to 90m resolution outside the USA.

the ASTER GDEM dataset has 30m resolution worldwide, wich is better.
ASTER DEM is distributed by the NASA and a Japanese organisation.

the dataset consists of GeoTiff format, so those would need to be converted to HGT.
Pre- requisites:
You will need the GDAL tools ( http://www.gdal.org/ ) to convert them. I suggest using linux as this is the easiest way to get them.

1/ Create an account there : https://reverb.echo.nasa.gov/reverb/users/new
2/ go there : http://gdex.cr.usgs.gov/gdex/ and sign in with the account you just created.
3/ select the area you want using the interface. there is a limit, so don't select over 300kmx300km or so.
4/ click the button "Download data", it is the last of the small ones at the top.
5/ A box pop up. Select "ASTER GDEM v2" and "Geotiff 1x1 tile", check .zip, choose a research area, and hit Submit
6/ Another box pop up after a few seconds, hit Download

Ok, you now have the files ! Now, we need to convert them to HGT, so Oruxmaps can read them.

7/ Download and install GDAL (on linux, it can be as simple as "apt-get install gdal-bin")
8/ for each ASTGTM2_N000E000_dem.tif file, execute this command:
gdal_translate -of SRTMHGT ASTGTM2_N000E000_dem.tif N000E000.HGT
(The numbers in red will be different for each files)

Copy all the HGT files in the oruxmaps/dem folder an it's done !

Yeah, it is a little tedious to execute the command for EVERY file, next step is writing a nice little shell/dos script that will handle that.

Info: each tile is about 25Mb and covers about 40km²

Thanks the NASA for making this data available !
On the old continent, this sort of data, even when 100% public-founded, is unavailable or sold for profit at best Evil or Very Mad so you pay twice the data, first with taxes, then with cash.
The french IGN has made available a DEM at a resolution of 250m (BD alti) in an act of goodwill. pathetic.



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Post  drmrbrewer Mon Dec 24, 2012 8:33 pm

Thanks for this tutorial. Very helpful.



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