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Sorry to come out so often with GMT solutions in this GDAL list but
somethings are so trivial there.<br>
<br>
If you can trust that all your negative values are (mean)seawater,
this will do the job<br>
<br>
grdclip yourGrid -Sb0/0 -Gclipped_grid.nc<br>
<br>
Note, one need the dev GMT5 version to read all grid formats through
GDAL, otherwise (GMT4) "yourGrid" should be netCDF<br>
<br>
Joaquim<br>
<br>
<blockquote
cite="mid:CALtm4h0RGQk0nSCEa+EjYmfUCbnWE8UbfyN10f6FpJHG35FQgg@mail.gmail.com"
type="cite">
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<div>
<div>Michael,<br>
<br>
</div>
I'm not sure if you can do this using one of the existing
utilities, you may be able to do this my creating a virtual
file (gdalbuildvrt) and modifying it see - <a
moz-do-not-send="true"
href="http://www.gdal.org/gdal_vrttut.html">http://www.gdal.org/gdal_vrttut.html</a>,
but I have not attempted this. An alternative is to do this
using the API and something like numpy to choose and rewrite
pixel values.<br>
</div>
See the following for a example in python <a
moz-do-not-send="true"
href="http://svn.osgeo.org/gdal/trunk/gdal/swig/python/samples/val_repl.py">http://svn.osgeo.org/gdal/trunk/gdal/swig/python/samples/val_repl.py</a><br>
<br>
<div> <br>
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<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On 9 January 2013 11:33, Smith, Michael
<span dir="ltr"><<a moz-do-not-send="true"
href="mailto:Michael.Smith@maine.gov" target="_blank">Michael.Smith@maine.gov</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div link="blue" vlink="purple" lang="EN-US">
<div>
<p class="MsoNormal">I have some DEMs that are created
from lidar. For reasons related to seeing currents
and wind effect, we did not ask for the water to be
flattened, but rather it shows waves. This is cool,
and what we wanted. BUT of course now we want to
create a second set of DEMs with a nice flat ocean.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">I have numerous pixels out in the
ocean which are slightly less than 0. So how does one
select out all pixels < 0 and substitute them with
0 with GDAL?
</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Times New
Roman","serif"">===============================<br>
</span><b><span style="font-size:10.0pt">Michael Smith
MS GISP</span></b><span style="font-size:10.0pt"><br>
State GIS Manager, Maine Office of GIS<br>
State of Maine, Office of Information Technology<br>
michael.smith _at_ <a moz-do-not-send="true"
href="http://maine.gov" target="_blank">maine.gov</a><br>
<a moz-do-not-send="true" href="tel:207-215-5530"
value="+12072155530" target="_blank">207-215-5530</a><br>
<br>
Board Member, Maine GeoLibrary<br>
Education Chair, Maine GIS Users Group<br>
State Rep, National States Geographic Information
Council<br>
</span><span
style="margin-left:0px;margin-top:0px;width:298px;min-height:67px"><img
src="cid:part6.00060102.09010109@ualg.pt"
height="67" width="298"></span><span
style="font-size:12.0pt;font-family:"Times New
Roman","serif""><img
src="cid:part7.00060302.03080808@ualg.pt"
alt="icons" height="68" width="299"></span><span
style="font-size:12.0pt;font-family:"Times New
Roman","serif""><br>
<br>
</span><span style="font-size:10.0pt">***NOTE NEW
ADDRESS***<br>
<br>
</span><span style="font-size:8.0pt">State House
Station 145<br>
51 Commerce Drive<br>
Augusta, ME 04333-0145<br>
69<sup>o</sup> 47' 58.9"W 44<sup>o</sup> 21' 54.8"N</span></p>
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