Joaquim,<br><br><div class="gmail_quote">On Wed, May 12, 2010 at 5:07 AM, Joaquim Luis <span dir="ltr"><<a href="mailto:jluis@ualg.pt">jluis@ualg.pt</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Hi,<br>
<br>
Before filling a ticket I would like to ask here if this gdalwarp behavior is the intended one.<br>
When I convert a grid from geogs to UTM the nodatavalues are filled with zeros.<br>
I get the expected behaviour if I use the -dstnodata with a numeric value, but I found no way tom tell it use NaN.<br>
<br>
Summary<br>
<br>
This puts zeros on the nodata zone, but I don't find it correct as "0" is not exactly a natural nodata value. For my habits NaN is the natural no data value.<br></blockquote><div>NaN should always be treated as a special case in coding. Imagine performing a type conversion.<br>
Since we usually deal with real world data, we know the data value range. We should be able to choose a nodata value not in the data range.<br><br></div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<br>
gdalwarp -s_srs "+proj=latlong" -t_srs "+proj=utm +zone=29 +datum=WGS84" swath_grid.grd lixo_utm.tiff<br>
<br>
Furthermore when I load the " lixo_utm.tiff" in Mirone is does not recognize a nodata value, whilst if I do this instead<br>
<br>
gdalwarp -s_srs "+proj=latlong" -t_srs "+proj=utm +zone=29 +datum=WGS84" -dstnodata 1 swath_grid.grd lixo_utm.tiff<br>
<br>
than "1" is recognized as the nodata. I have not investigated the metadata to see why the "0" is not set to represent the nodata.<br></blockquote><div>Perhaps swath_grid.grd doesn't have a nodata value set.<br>
</div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<br>
Thanks<br><font color="#888888">
<br>
Joaquim Luis<br>
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</font></blockquote></div><br><br clear="all"><br>-- <br>Best regards,<br>Chaitanya kumar CH.<br>/tʃaɪθənjə/ /kʊmɑr/ <br>+91-9848167848<br>17.2416N 80.1426E<br>