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r.watershed: Use raster mask, not MASK, simplify doc #4998

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Jan 29, 2025
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r.watershed: Use raster mask, not MASK, simplify doc #4998

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r.watershed: Use raster mask, not MASK, simplify doc
wenzeslaus Jan 27, 2025
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Merge branch 'main' into r_watershed-mask-not-MASK
petrasovaa Jan 28, 2025
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16 changes: 7 additions & 9 deletions raster/r.watershed/front/r.watershed.html
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Expand Up @@ -316,17 +316,15 @@ <h3>Basin threshold</h3>
stream segment is determined by the distance between the tributaries
flowing into it.

<h3>MASK and no data</h3>
<h3>Masking and no data</h3>


The <em>r.watershed</em> program does not require the user to have the
current geographic region filled with elevation values. Areas without
elevation data (masked or NULL cells) are ignored. It is NOT necessary
to create a raster map (or raster reclassification)
named <code>MASK</code> for NULL cells. Areas without elevation data will
be treated as if they are off the edge of the region. Such areas will
reduce the memory necessary to run the program. Masking out
unimportant areas can significantly reduce processing time if the
elevation data (masked or NULL cells, i.e., no data) are ignored and
treated as if they were outside the region. Masking out
unimportant areas can significantly reduce processing time and memory
requirements if the
watersheds of interest occupy a small percentage of the overall area.

<p>
Expand Down Expand Up @@ -357,7 +355,7 @@ <h3>Further processing of output layers</h3>
module, a number of approaches may be considered.

<ol>
<li>Use a resample of the basins catchment raster map as a MASK.<br>
<li>Use a resample of the basins catchment raster map as a raster mask.<br>
The equivalent vector map method is similar
using <em><a href="v.select.html">v.select</a></em> or
<em><a href="v.overlay.html">v.overlay</a></em>.</li>
Expand Down Expand Up @@ -386,7 +384,7 @@ <h3>Further processing of output layers</h3>
with
<em><a href="r.thin.html">r.thin</a></em>. Each stream segment in the
vector map will have the value of the associated basin. To isolate
subbasins and streams for a larger basin, a MASK for the larger basin
subbasins and streams for a larger basin, a mask for the larger basin
can be created with
<em><a href="r.water.outlet.html">r.water.outlet</a></em>. The stream
segments output serves as a guide where to place the outlet point used
Expand Down
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