This gdal command mosaics all SRTM-Tiles into on bi geotiff. This is what I use for SRTM-Display. Performance is good (equla to using tiles), and you don't need to care about managing all the tiles on your server:

gdal_merge -of GTiff -co "TILED=YES" -co "COMPRESS=LZW" -co "BIGTIFF=YES" -ot Int16 -n -32768 -v -o srtm41.tif tiff/*.tif


Make sure, you have all your srtm tiles downloaded and stored in ./tiff.

The command created a 16-bit image, compresses it, applies tiling and all the good stuff.


You also want to build overviews for display speed, so issue this command subsequently:

gdaladdo -r cubic srtm41.tif 4 8 16 32 64 128 256 512

This will create the image pyramids srtm41.tif .

Cheers,
Matthias

Am 14.11.2011 11:01, schrieb Ákos Maróy:
On 13/11/11 23:58, [email protected] wrote:
I would suggest you do a conversion of the SRTM files to GeoTIFF.  Chances
are very good you can do this with gdal utilities
http://www.gdal.org/gdal_utilities.html .

thanks for the tip. I tried, and it doesn't really look good - after the
conversion, the file seems to 'lose depth'.

when I open the converted .tif file in gimp, it tells me that the file
uses 16 bit channels, while gimp only supports 8 bit channels. and thus
the depth of coloring in the file is very crude.

and I get the same effect when viewing the resulting layer, after
importing it into geoserver, using the built-in OpenLayers preview.

OTOH, when converting the HGT file into a JPEG using gdal, it seems to
preserve all information.

might it be that GeoServer supports only 8-bit GeoTIFF files, whereas
the HGT files contain 16 bit height information?

Recursion is not directly supported but could be easily done through the
REST interface
http://docs.geoserver.org/stable/en/user/restconfig/index.html

Examples are here:
http://docs.geoserver.org/stable/en/user/restconfig/rest-config-examples/index.html

thanks - this would solve the issue of importing a number of files.
OTOH, is it easy to combine these files into a single layer somehow? or
should combine the GeoTIFF files in advance, and import it as one big file?

There is a built in preview that shows the data through OpenLayers in a
browser.

thanks for the tip!

5. maybe I'm missing something, and there is a better source of
elevation data available than SRTM?

Ah, well that's a harder question-- it depends upon your geography.  Other
similar near global sources include ASTER sources.

thanks for the tip. this seems to offer more detailed data (1/3 arc sec
instead of 1 - 3 arc sec), but I can't find a comprehensive download
option for the whole data set, only an interactive one for selective
download. will look further..


Akos

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