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I have two questions related to calculate building density.

  1. I need to calculate the building density in a map which Data is in shape format. The buildings and the area are in two different layers.

  2. Same question as above but the map/area is raster format.

Thank you.

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Is this homework? :) –  blah238 May 22 '12 at 5:38
Kind of,but rather semester work, i was trying to do it by myself. i m not unfortunatelly the specialist in ArcMap:) –  user7678 May 23 '12 at 10:40
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1 Answer

Before you begin you need to define what you mean by 'building density'. Do you mean buildings per unit area or do you mean the area covered by building footprints per unit area? These are not the same thing. The former might be more appropriate if you are looking at (say) ownership but takes no account of the difference in size of building.

Consider two towns. One has a few huge buildings and the other has many small buildings. The land area covered in each case is identical but the number of buildings per unit area is radically different.

Next, how are you defining 'building'. Is a row of terraced houses, a single building or multiple buildings? If you say 'It must be multiple buildings because it has multiple owners and multiple front doors', what about flats/apartments? Also, you could equally argue that a terrace should be considered to be a single building because it was designed as a single unit by the architect.

To continue, many might consider building denisty in a downtown area to be higher than in a semi-suburban area. They may be right in literal terms but then again, many suburbs can have as much ground coverage as the downtown area but be considered less dense because they are lacking in the third dimension (building height). OK, that last point is legitimate but stretching things a tad. However, I'm trying to make it clear that mapping 'density' is not quite as straight forward as may first appear and that your definition of 'density' will change the way you do your analysis. On that note have a look at this video.

ONE way to approach for each of your questions are as follows (there are others and, like I say, much depends on your definition of density):

  1. Convert the building footprints to points and then calculate point density (this is like my first example above).
  2. Get the number of raster cells coded as buildings, multiply by the resolution and then divide by the total area of your raster (this will tell you nothing about clustering, auto correlation etc though).

You need to read up on spatial statistics for a full answer, but a trawlthrough the capabilities of Spatial Analys extension will be an excellent start.

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Thank Your fot the answer. –  user7678 May 23 '12 at 20:06
Thank Your fot the answer. Of coruse i know, that there are more kinds of density. I need exactly: area covered by building footprints per unit area. The problem is i have the bulding as polygons and in another layer the reference area. I dont know exactly how can i count this density if they are on different layers. And in this case it think i can not use the point density. And in the second task i should use point density in refernce to raster –  user7678 May 23 '12 at 20:21
For the vector calculation, can't you simply add up the areas of the building footprint polygons that lie within (completely? intersect?) the study area polygon and divide that by the area of the study area polygon? –  blah238 May 24 '12 at 3:32
Yes, yes i did it already, after some hours trying. But i know it s not exactly that what my prof. expect. –  user7678 May 24 '12 at 9:16
But lets say this is ok. But next problem i have with raster. cause there u dont know exactly how to "get the number of raster cells coded as buildings". With raster format we didnt have any lectures, thats why it s a kind of problem for me. –  user7678 May 24 '12 at 9:42
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