[osg-users] vpb and GTOPO30

Ümit Uzun umituzun84 at gmail.com
Mon Sep 1 02:30:55 PDT 2008


Hi Cedric,

I use another elevation data which are grayscale images. To create a good
height relief whole earth database;

1 - Open up the ftp://veftp.gsfc.nasa.gov/bluemarble/ and download
land_shallow_topo_west.tif and land_shallow_topo_east.tif

2 - Open up the http://visibleearth.nasa.gov/view_detail.php?id=8391 and
download srtm_ramp2.world.21600x10800.jpg (P.S. You can download
srtm_ramp2.world.86400x43200.bin.gz.torrent or
srtm_ramp2.world.5400x2700.jpg but I created my earth database with using
srtm_ramp2.world.21600x10800.jpg)

3 - Use "gdal_translate srtm_ramp2.world.21600x10800.jpg
topo_unreferenced.tif" command to convert jpg to tiff format.

4 - At this point created topo_unreferenced.tif image hasn't WGS84 reference
meta-data. So we dig in these data with using gdal_vrt files. For
topo_unrefereced.tif images our vrt file is like below;

------------------------------reference.vrt----------------------------
<VRTDataset rasterXSize="21600" rasterYSize="10800">
<SRS>WGS84</SRS>
<GeoTransform>180,0.016666666666666666,0,90,0,
0.016666666666666666</
GeoTransform>
<VRTRasterBand dataType="UInt16" band="1">
<ColorInterp>Gray</ColorInterp>
<SimpleSource>
<SourceFilename>topo_unrefereced.tif</SourceFilename>
<SourceBand>1</SourceBand>
<SrcRect xOff="0" yOff="0" xSize="21600" ySize="10800"/>
<DstRect xOff="0" yOff="0" xSize="21600" ySize="10800"/>
</SimpleSource>
</VRTRasterBand>
</VRTDataset>
------------------------------reference.vrt----------------------------

5 - Copy and paste the reference.vrt xml data to the notepad and save on
your disk.

6 - Use "gdal_translate referance.vrt topo_referenced.tif" command. This
command create you topo_referenced.tif real whole earth elevation data.

7 - osgdem --bluemarble-east -t land_shallow_topo_east.tif --bluemarble-west
-t land_shallow_topo_west.tif --geocentric -o earth/earth.ive -so
build.source

8 - osgdem -s build.source -d topo_referenced.tif -v 750.0 -l 6

9 - After build operation you should get well height relief whole earth
database.

If any problem you get while the operation, only ask me.

Best Regards.

Ümit Uzun
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