[gdal-dev] Attempting to merge DEMs with gdal_merge.py - getting Float32 clipped to 255.0

[Chaitanya kumar CH]

Michal,

Check if the output file already exists. The script won't create a new one
if it already exists.

On Mon, May 16, 2011 at 12:45 AM, Michal Migurski <mike at stamen.com> wrote:

> Hello,
>
> I'm attempting to merge a number of DEMs in .flt format using
> gdal_merge.py. It's NED 1/3 arc second data, so each one is a Float32
> 10812x10812 raster with a range of values from a few meters below sea level
> to 1.4km. I'm getting back an image with an incorrect datatype even though I
> believe that I'm using the right "-ot Float32" parameter to gdal_merge.py. I
> appear to have gdal 1.5.4 on this machine; I can upgrade to a newer one if
> necessary but I'd first like to make sure I'm not using the tool
> incorrectly.
>
> Here's the command I use:
>
>        gdal_merge.py -o 38122.tif -of GTiff -ot Float32 -v -ul_lr -122.05
> 38.05 -121.95 37.95 10m/*.flt
>
> What I get back is a 1080x1080 GeoTIFF with the correct bounds that I'm
> expecting, but what appears to be garbage data or perhaps just raw floating
> point values misinterpreted as bytes. Here's the output showing Byte values
> instead of Float32 as I'd expect:
>
>        Band 1 Block=1080x7 Type=Byte, ColorInterp=Gray
>          Min=0.000 Max=255.000
>          Minimum=0.000, Maximum=255.000, Mean=108.657, StdDev=66.615
>
> This is a sample of the resulting image in pseudocolor, showing the
> vertical banding every 4px that makes me think the bytes are just a raw
> Float32 stream:
>
>        http://mike.teczno.com/img/38122-rainbow.png
>
> Here is a sample input band:
>
>        Band 1 Block=10812x1 Type=Float32, ColorInterp=Undefined
>            Computed Min/Max=-8.170,1440.937
>          NoData Value=-9999
>
> Am I using -ot incorrectly?
>
> -mike.
>
> ----------------------------------------------------------------
> michal migurski- mike at stamen.com
>                 415.558.1610
>
>
>
> _______________________________________________
> gdal-dev mailing list
> gdal-dev at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/gdal-dev
>



-- 
Best regards,
Chaitanya kumar CH.
/tʃaɪθənjə/ /kʊmɑr/
+91-9494447584
17.2416N 80.1426E
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.osgeo.org/pipermail/gdal-dev/attachments/20110516/d7aeac25/attachment.html