Dear Visitors:

Please scroll down the page to see present and archive blogs.

Thank you very much: Tramway Null(0)

Webrings - Maps - Trolleys and More

Navigation by WebRing.

Wednesday, November 20, 2013

Some Grass 6.4.1 Visibility Experiments using the Kolumna Zygmunta at Castle Square Warsaw

Castle Square or Plac Zamkowy is a historic square in Warsaw Poland and has an interesting Column going back many years which has been rebuilt many times.  The historic column is called the Kolumna Zygmunta in Polish and was built in honor of King Sigismund III.  It is 22 meters high and it would be interesting to do some visibility experiments with it using GRASS 6.4.1 in the raster mode.  To do this experiment, I will ask you to envision that no buildings exist in Warsaw except this beautiful monument.  How far can we see this monument in the distance?  It depends on the changes in elevation in altitude of the surroundings.  I was able to bring into GRASS 6.4.1 a raster file based on the elevation of entire Poland.  According to what I have seen, Warsaw is relatively flat.  In other parts of the experiment, we will do a thought experiment:  What would happen if the Kolumna Zygmunta would be as tall as the new World Trade Center in New York at 1776 feet?  How far would a resident of Warsaw or Poland see it?   In this experiment, I do not take into effect the curvature of the earth and I used various ranges, between 20,000 meters and 90,000 meters.  Well lets get to it.  Please ignore the scale bar, it is incorrect and I cannot remove it.

In this experiment, the using the raster visibility option, the height of the column was raised to 541 meters, which is the height of the World Trade Center.  Not taking into consideration the curvature of the earth, the column would be observable throughout Poland except in the white areas.  I do not know the reason for this.  In the south, it would be visible at selected high elevations.  The range is set to 90,000 meters.
In this map above, I brought in a shape file (vector) of important roads in Warsaw.  The red square is the location of the column.  The yellow coloring shows where in Warsaw a 1776 foot Kolumna Zygmunta would be visible.  It would be visible of course, throughout Warsaw, but I cannot give a reason for the few white gaps in the map.  These white gaps do not correspond to high elevations.
In the map above, I set the Kolumna Zymunta height to 22 meters, its actual height.  If no buildings were blocking the view, or if you were looking down a wide boulevard, there would be gaps in Warsaw were the monument would not be visible.  The red areas are higher elevations outside of Central Warsaw.  Range is 30,000 meters.
In the map below, I used the option in GRASS to correct for the curvature of the earth for the visibility scenario at the Kolumna Zygmunta with the incredible height of 1776 feet.
 The central Warsaw area is indicated by the rectangle.
In the map below, I used an option to create a map based on  elevations that are based on a density function:
The Central area of Warsaw is indicated in red.

No comments:

Post a Comment