Calculating Visibilty atop Riga's Freedom Monument using GRASS 6.4.1.

  What would I see if I placed a camera atop of Riga's Freedom Monument?  Using GRASS 6.4.1. I used as an input the coordinates of 56.57 and 24.647 and I listed the height of the viewer at 42 meters, the height of the monument.  I used the default range of 100000 meters and the results are shown above.  It seems to me that most of the country would be visible?  Notice that the thin lines, which are either railroads or roads that I added as shapefiles to the map, have no images around them.  Perhaps these roads and railways are at lower elevations?  At any rate, I cannot understand the results and perhaps I did something wrong, but it was interesting to do this experiment.  Notice that for one of the pictures, I choose one with trolleybus and tram wires!  The results indicate as follows:  If I was standing atop of the Freedom Monument and if no buildings blocked my view and I was able to see the flat surface of the earth, I would see most of the yellow areas extensively into the interior and I would see higher elevations (in red) in the distance (over 150 meters high).  I would also see the island area across the water.  Of course, the buildings in Riga would block my view because this calculation was based on natural elevations only and did not take into effect the height of surrounding buildings.  The white areas would be hidden because they are low or because they are behind a high elevation area.