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Wednesday, August 29, 2012

Calculating Visibility from the Smith-9th Street Station in Brooklyn using GRASS 6.4.1.

In the attached map, New York Subway station and lines were brought in to produce a map.  The street elevation level was added and GRASS 6.4.1 terrain analysis was conducted to produce the visibility to the street surface from the station itself, which is about 90 feet tall.   The x-y coordinate I used was 985286.93, 184579.87   The green area on the map shows the area, if buildings were not in the way, how far an observer will see the surface.  Of course, you can see much further than the green area if you are looking at tall buildings and other structures.  Notice that the visibility area is not circular because the surface has hills in it that would block the observer's view.

These pictures were taken off the web.  The top picture is serveral years old and shows a southbound R-46 F train approaching the Smith-9th Street after leaving the the tunnel at Carroll Street.  The second picture is also off the web and was taken from the same station and is facing north showing the Culver Viaduct declining into the Carroll Street Station.  Notice the buildings on the hill west of the viaduct.  The above picture shows the viaduct above the Gowanus Canal. The station is above the canal and runs to the right.  Notice that on the terrain analysis diagram, the hill in Carroll gardens is blocking the view of the surface (non green area) , just like in the photograph.

   In the map below, the same GRASS 6.4.1 procedure was run,  except that the range was expanded to 700,000 meters.  I do not know why the analysis stops in middle of the harbor.  The Smith-9th Street station is found on the map as a red X.

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