[postgis-users] Simple Line Density

[Jeff Adams - NOAA Affiliate]

Hi John,

ArcGIS offers a similar type of analysis (summing length of lines in each
raster cell) for line density. This is definitely a useful measure.
Wouldn't mind if I could do both. I am looking at the density of marine
vessel transits with goal of trying to see where vessel routes are
concentrated. For this particular analysis, I am not really interested in
the amount of any particular transit in a cell, just that it was there. I
suppose the sum of line lengths can serve as a proxy, but in a perfect
world, I would be able to create a raster whose values represent the number
of transits. Thanks for the response and happy holidays...

On Mon, Dec 24, 2012 at 9:39 AM, John Callahan <john.callahan at udel.edu>wrote:

> I had the same problem.  I ended up using the Quantum GIS function, Sum
> Line Lengths.  Input can be your postgis line features.  It adds up the
> lengths of the portion of each line that crosses a particular grid cell.
>  You need to create a polygon fishnet matching your raster extent and
> resolution first, then convert to raster.  This might actually be a better
> measure of density then counting lines.
>
> - John
>
>
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