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<div class="moz-cite-prefix">On 07/17/2018 01:12 AM, Rich Shepard
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:alpine.LNX.2.20.1807161459240.23050@salmo.appl-ecosys.com">On
Mon, 16 Jul 2018, Rich Shepard wrote:
<br>
<br>
<blockquote type="cite">This suggests that the solution is to
create a mask and generate the
<br>
contours only within that area.
<br>
</blockquote>
<br>
In the monitor I displayed the DEM and a couple of reference
vectors, then
<br>
zoomed to an area within which I want to create a vector area to
use as a
<br>
mask. I've not found a method that lets me do this interactively.
<br>
<br>
First, I tried a vector map edit and gave it the name
'analysis_area'. The
<br>
monitor removed the current display and left a white board on
which to draw,
<br>
but I had no reference points because the raster DEM and vector
features
<br>
were not visible.
<br>
<br>
Second, I tried a raster map edit and provided the same name
along with
<br>
the raster DEM as a background. This produced a white rectangle in
the
<br>
middle of the display and again I could not see the background so
I could
<br>
not draw an area boundary.
<br>
<br>
What is the proper process to use a displayed map while drawing
an area
<br>
boundary (vector, or raster that can be converted to a vector) and
seeing
<br>
where the edits are located?
<br>
</blockquote>
I don't think there's any need for manual editing. What I do is
change the regions settings to the area of interest. Then almost all
raster calculations work only inside that region. So:<br>
<br>
<font size="+1"><tt># First save the current settings for restoring
later</tt><tt><br>
</tt><tt>g.region save=FULL_REGION</tt><tt><br>
</tt><tt># Now reduce the region (leave the resolution as is)</tt><tt><br>
</tt><tt>g.region -ap n=<max y> s=<min y> e=<max
x> w=<min x></tt><tt><br>
</tt><tt># Do your stuff</tt><tt><br>
</tt><tt>r.contour input=<your DEM> output=contours</tt><tt><br>
</tt><tt># If you really need a vector rectangle bounding the
small analysis area region then</tt><tt><br>
</tt><tt>v.in.region output=analysis_area</tt><tt><br>
</tt><tt># In future you get back to this smaller region with
g.region -ap vect=analysis_area</tt><tt><br>
</tt><tt><br>
</tt><tt># Now, if necessary, return to the full region with</tt><tt><br>
</tt><tt>g.region -ap region=FULL_REGION</tt></font><br>
<br>
<blockquote type="cite"
cite="mid:alpine.LNX.2.20.1807161459240.23050@salmo.appl-ecosys.com">
<br>
Rich
<br>
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</blockquote>
<br>
<pre class="moz-signature" cols="72">--
Micha Silver
Ben Gurion Univ.
Sde Boker, Remote Sensing Lab
cell: +972-523-665918</pre>
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