I am trying to calculate the road density in my study landscape. I am using the spatial analyst, and the line density function. By default, the tool is setting a cell size of 3.6km*3.6km, and the window to 30819. The results look correct visually (high density of roads show up as such), but the values dont make sense. The range is from 0-.23, which I am interpreting as .23 km per 12.96km2. These values are very very low, and are definitely not correct. Am I making a very big oversight? The projection is in WGS_1984_World_Mercator, and the study site is in India.

  • Wouldn't you be creating a fishnet of your cells, intersecting with roads and then summary statistics of shape_length (sum) with case field of fishnet id? Note: shape_length would be metres, you'd need to divide the result by 1000. What do you define as density of road? is it percent of area that is road or km of linear road per cell? – Michael Stimson Dec 18 '14 at 5:24
  • Road density for my case means km of roads/km2 area. – Trishna Dec 18 '14 at 5:29
  • Try the fishnet/intersect/summarize method. I know for a fact that this will give you a true result which you can compare against your raster method to verify or disprove your findings. – Michael Stimson Dec 18 '14 at 5:32

in my point of view, you should decide your unit area (it could be county boundary or certain grid). after that, do some geoprocessing to divide roads in each unit area. Then you calculate each of roads length in each unit area and divide with the hectarage (or km2).

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EDIT : The default output of line density is in kilometer per square kilometer. So the output of the tool is already what you are looking for (you don't need to divide it again by the size of the circle, this is done automatically).

Note that the vector-based approach from @Anggik will be more precise, however you will not have overlapping window analysis.

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  • Radouxju, I conducted the raster analysis and focal statistics. My values now range from 0-9. Im not sure how to interpret the values. The pixel size is 3.7km X 3.4km. – Trishna Dec 18 '14 at 10:11
  • @Tishna sorry, I was confusing point and line density. I have updated my answer. – radouxju Dec 18 '14 at 11:43

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