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@@ -19,20 +19,20 @@ Cells containing null data will be marked with an "X".
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You can disable drawing of null data and unknown aspect values by
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setting its color to "<tt>none</tt>".
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-<p>If you specify the <em>magnitude_map</em> option, arrow lengths
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-denoting magnitude will be extracted from the cell values of the specified
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+<p>If you specify the <em>magnitude_map</em> option, arrow lengths
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+denoting magnitude will be extracted from the cell values of the specified
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map. In this case the tail of the arrow will be centered on the source cell.
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You may adjust the overall scale using the <em>scale</em> option.
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<em>d.rast.arrow</em> will ignore NULL and negative magnitudes, and will
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warn you if the debug level is set at 5 or higher. Be aware. If your application
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uses negative values for magnitude, you can use
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<em><a href="r.mapcalc.html">r.mapcalc</a></em> to prepare the magnitude map to
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-suit your needs (absolute value, inverted direction and so on).
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+suit your needs (absolute value, inverted direction and so on).
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<p><h2>NOTES</h2>
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-By default, arrows are drawn at the size of a cell and cannot be seen if
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-the raster map is relatively close in scale. You can use the <em>skip</em>
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-option to draw arrows every n-th cell in both directions if you are working
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+By default, arrows are drawn at the size of a cell and cannot be seen if
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+the raster map is relatively close in scale. You can use the <em>skip</em>
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+option to draw arrows every n-th cell in both directions if you are working
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with relatively high resolutions. It may be useful to disable the grid in
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this case, which is accomplished by setting its color to "<tt>none</tt>".
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<p>For GRASS and Compass type aspect maps, the cell values of the aspect map
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@@ -56,15 +56,15 @@ counterclockwise from east. e.g.:
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They can be created from a raster elevation map with
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<em><a href="r.slope.aspect.html">r.slope.aspect</a></em>.
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<p>Compass type aspect maps are measured in degrees clockwise from north.
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-<p>This module uses oceanographic conventions, i.e. arrows point downslope or
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+<p>This module uses oceanographic conventions, i.e. arrows point downslope or
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direction "to", as opposed to atmospheric conventions (direction "from").
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<h2>EXAMPLE</h2>
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-Convert U,V velocity component maps into magnitide,direction maps for use
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+Convert U,V velocity component maps into magnitide,direction maps for use
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with <em>d.rast.arrow</em>:
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-
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+
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<div class="code"><pre>
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r.mapcalc "magnitude = sqrt(U_map^2 + V_map^2)"
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r.mapcalc "direction = atan(U_map, V_map)"
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@@ -90,7 +90,7 @@ Chris Rewerts<br>
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Purdue University</em><br><br>
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<u>Magnitude and 360 arrow code</u><br>
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Hamish Bowman<br>
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-<em>Department of Marine Science, <br>
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+<em>Department of Marine Science,<br>
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University of Otago, New Zealand</em><br><br>
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<u>Align grids with raster cells and Drainage aspect type</u><br>
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Huidae Cho<br>
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Huidae Cho