Am 11.12.12 14:51, schrieb Christian Schmitt:
> Adrian Musceac wrote:
>
>> I really hope my toolchain will work on the next issue of terragear :)
>> Do we still have terrafit which outputs .fit.gz, and ogr-decode does
>> function the same way? Right now I'm on the right path, but it's bumpy.
>> I think there's a real need for a LOD system, or another system which
>> would allow loading terrain as far as 300 km away, perhaps without adding
>> at load time random elements, lights, and stuff. Unfortunately I'm not
>> very familiar with OSG database pagers and the underlyings in simgear.
>>
>
> Hi Adrian,
>
> generally, yes a LOD system would be nice, but it would need considerable
> changes on the btg format or a switch to something new.
> I'm currently investigating how to make elevation calculation for the
> terrain easier and more versatile. I want to use gdalchop for general
> processing as gdal reads almost all kinds of raster formats. So we would no
> longer have to rely on hgtchop, srtmchop and demchop (yes, it's mad).

Hi Christian

Nice to hear that there are some plans (?) with extending gdalchop. As I 
mentioned earlier I’m preparing 5x5 degree tiles of all the SRTM data in 
geotiff format to use with terragear (just in case someone wants to give 
it a try once, I use it for my reliefs and this 5x5 tiles are a side 
effect of processing this data). A 5x5 degree geotiff uncompressed will 
have around 72 MB.

When it’s useful and gdalchop can handle this I can prepare the data 
with LZW compression, which makes it a bit faster, at least for the 
download ;-) Recently the compressed geotiff files will take about 25-30 
GB for the "HGT-SRTM-World" coverage.

The tiles have 6001 x 6001 pixels in EPSG:4326 projection. For the 
reliefs I needed to reproject the data to other projections (EPSG:3857 
or i.e. 3112) and I used gdalwarp for this with lanczos interpolation, 
which gives me the best results for reliefs. Iin a graphical sense of 
course, I don’t know if it would be also the case for other purpose with 
lanczos.

-Yves



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