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@@ -29,8 +29,9 @@ visible or the respective point in the elevation map is NULL.
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Otherwise, a value in [0, 180] representing the vertical angle with
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regard to the viewpoint, in degrees, if the point is visible.
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-0 degrees: directly above the observer,
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-180 degrees: directly below the observer
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+A value of 0 is directly below the specified viewing position,
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+90 is due horizontal. The angle to the cell containing the viewing
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+position is undefined and set to 180.
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<p>
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If the <b>-b</b> flag is set, the output is in boolean-mode, and each point
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@@ -71,7 +72,7 @@ the terrain. The user can change this using option
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elevation.
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<p>
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-By default the target is assumed to have height 0 map units above the
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+By default the target is assumed to have height of 0 map units above the
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terrain. The user can change this using option
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<b>tgt_elev</b> to determine if objects of a given height would be
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visible. The value entered is in the same units as the elevation.
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Markus Neteler