Add doc.

Author: abellgithub

alg/viewshed/viewshed_executor.cpp

@@ -148,7 +148,17 @@ ViewshedExecutor::ViewshedExecutor(GDALRasterBand &srcBand,
     m_hasNoData = hasNoData;
 }
 
-// No SD Band
+/// Constructor - the viewshed algorithm executor with no SD band
+/// @param srcBand  Source raster band
+/// @param dstBand  Destination raster band
+/// @param nX  X position of observer
+/// @param nY  Y position of observer
+/// @param outExtent  Extent of output raster (relative to input)
+/// @param curExtent  Extent of active raster.
+/// @param opts  Configuration options.
+/// @param progress  Reference to the progress tracker.
+/// @param emitWarningIfNoData  Whether a warning must be emitted if an input
+///                             pixel is at the nodata value.
 ViewshedExecutor::ViewshedExecutor(GDALRasterBand &srcBand,
                                    GDALRasterBand &dstBand, int nX, int nY,
                                    const Window &outExtent,