kpzimmer

Incorrect Results from Line Density Tool

Discussion created by kpzimmer on Sep 4, 2013
Latest reply on Sep 5, 2013 by xander_bakker
Hello,
I am trying create a raster that shows road density (m/ha) within 3km radius of the cell.  The line density tool in Spatial Analyst appears to be the tool to do this as it allows for input of a line file (roads), a search radius (3000m), output raster cell size (10m), and area unit (ha). However, upon running the tool I getting results that I don't believe to be correct. For example the maximum value I am getting is 0.27 m/ha, which is way to low of a value considering to the high road density in the area. To double check I converted a portion of the raster to points and buffered those points by 3 km and found the area of road within this buffer. Using this information the road density values come out to around 9 or 10 m/ha which is much more reasonable for the density of roads in the area. The dataframe and road layer is in UTM Zone 12N so the units should be in meters. Any ideas why these results are not correct? I wonder if it has to do with the population field being set to none as in the tool help it indicates the population field is a:

Numeric field denoting population values (the number of times the line should be counted) for each polyline.
Values in the population field may be integer or floating point.

The options and default behaviours for the field are listed below.
Use None if no item or special value will be used and each feature will be counted once.

Therefore I'm wondering if it is only counting each road line feature the first time it intersects a cell search radius instead of counting it within the search radius of each cell.

Any advice or suggestions would be greatly appreciated. Below is my inputs if that helps. Thanks in advance.

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