[postgis-users] Simple Line Density

Jeff Adams - NOAA Affiliate jeff.adams at noaa.gov
Sat Dec 22 18:57:55 PST 2012

Thanks for the response Stephen.I will have upwards of 150,000 lines
features that I will want to feed into the density. These are stored in a
single table (actually will be in a CTE), and many of the lines will
overlap one another. It is hard to say whether these solutions are viable
as I am having a hard time visualizing the SQL. You would think that I am
not the first person who has wanted to do this in PostGIS, but I haven't
found example one.

On Sat, Dec 22, 2012 at 6:02 PM, Stephen Woodbridge <woodbri at swoodbridge.com
> wrote:

> On 12/22/2012 3:07 PM, Jeff Adams - NOAA Affiliate wrote:
>> Hi,
>> I was wondering if anybody knew of a way to create a very simple line
>> density raster. I am not interested in interpolation or clustering,
>> simply how many line features pass through each pixel in the raster. I
>> know how to do this with points, but am having difficulty figuring out
>> how to do it with lines. Any help would be greatly appreciated...
> Separate from the SQL, you probably need to have a strategy for doing
> this. so with a point I assume you just increment the point in the raster
> for each point. So with a line we want to increment the all the raster
> points along the line. Some options:
> 1. render the line into an empty raster then add that raster to your
> master raster. Where add will increment by one every set  raster point in
> the rendered line.
> 2. segmentize the line into segments that are the size of a pixel in your
> master raster and then add the midpoints of those segments to your master
> raster.
> Would one of these work for you?
> -Steve
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Jeffrey D. Adams
OAI, Inc.
In support of:
National Marine Fisheries Service
Office of Protected Resources
1315 East West Hwy, Building SSMC3
Silver Spring, MD 20910-3282
phone: (301) 427-8434
fax: (301) 713-0376
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