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<div class="moz-cite-prefix">On 29/05/2014 16:42, Mark Seibel wrote:<br>
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cite="mid:CADHQGE3ji=Vf+_dmf35wt9TSnYdaK=5iG1h7bdD5Ru_QKahU9w@mail.gmail.com"
type="cite">
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<div class="gmail_extra">Hi.<br>
<br>
<div class="gmail_quote">On Thu, May 29, 2014 at 9:25 AM,
Randal Hale <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:rjhale@northrivergeographic.com"
target="_blank">rjhale@northrivergeographic.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">I have
two Digital Elevation Models - Imagine a square cut into
two equal triangles.<br>
<br>
No matter how I do it - One DEM overwrites the other one
so I'm only ever getting half of the elevation model I
want when I merge them.<br>
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<div>... </div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
Thoughts or ideas?<br>
<br>
Randy<br>
<br>
<br>
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<div>Is there a GRASS function in QGIS for r.patch? It uses
both datasets, and uses one to fill the NULL values of
another. Would probably have to make sure the
computational region is set to accommodate the extent of
merging both DEMs (maybe not necessary if r.patch doesnt
regard region settings).</div>
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<br>
The way to do this in GRASS is with the isnull() function in
r.mapcalc<br>
Here's an example from the man page:<br>
<br>
<p>
Example: The users wants the NULL-valued cells to be treated like
zeros. To
add maps A and B (where B contains NULLs) to get a map C the user
can use a
construction like:</p>
<p>
</p>
<div class="code">C=A + if(isnull(B),0,B)
<br>
<br>
<br>
And,as Mark mentioned, be sure to set your region to cover both
maps from the start<br>
</div>
<br>
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cite="mid:CADHQGE3ji=Vf+_dmf35wt9TSnYdaK=5iG1h7bdD5Ru_QKahU9w@mail.gmail.com"
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<div class="gmail_quote">
<div>Mark</div>
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<br>
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<br>
<br>
<pre class="moz-signature" cols="72">--
Micha Silver
GIS Consulting
052-3665918
<a class="moz-txt-link-freetext" href="http://www.surfaces.co.il">http://www.surfaces.co.il</a>
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