[postgis-users] Simple Point Density Surface

[Doug_Newcomb at fws.gov]

James,
        Looking at  - 
http://webhelp.esri.com/arcgiSDEsktop/9.3/index.cfm?TopicName=How%20Point%20Density%20works
.  Why not convert the raster cell centers to points , do a query on the 
point layer for a square centered on the raster derived point  whose 
dimensions are given by the number of tiles in your neighborhood.  return 
the number of points divided by the area of the square.  ( neighborhoods 
are usually odd numbers of cells, 3x3, 5x5, etc so you have an equal 
number around the center cell)  . 

        The kernel optoin requires more thought

Doug

Doug Newcomb 
USFWS
Raleigh, NC
919-856-4520 ext. 14 doug_newcomb at fws.gov
---------------------------------------------------------------------------------------------------------
The opinions I express are my own and are not representative of the 
official policy of the U.S.Fish and Wildlife Service or Dept. of the 
Interior.   Life is too short for undocumented, proprietary data formats.



JamesH <james.holmes at newcastle.ac.uk> 
Sent by: postgis-users-bounces at postgis.refractions.net
04/25/2012 01:15 PM
Please respond to
PostGIS Users Discussion <postgis-users at postgis.refractions.net>


To
postgis-users at postgis.refractions.net
cc

Subject
[postgis-users] Simple Point Density Surface






Hi all,

I am looking to take a point dataset and generate a point density raster 
in
PostGIS, similar to the ArcGIS Point Density tool in Spatial Analyst.

What I believe I need to do is to define a neightbourhood around each 
output
raster cell centre and calculate a density value for each pixel based on 
the
number of points that fall within that neighbourhood.

Ideally to recreate the same results, I would like to define a 
neighbourhood
with a radius of 8 cells - most likely a square neighbourhood.

I have been considering this for a while but I really cannot understand 
how
to acheive this.

Any advise or help would be greatly appreciated.

Kind Regards,
James Holmes

-----
GIS Undergraduate
--
View this message in context: 
http://postgis.17.n6.nabble.com/Simple-Point-Density-Surface-tp4917343p4917343.html

Sent from the PostGIS - User mailing list archive at Nabble.com.
_______________________________________________
postgis-users mailing list
postgis-users at postgis.refractions.net
http://postgis.refractions.net/mailman/listinfo/postgis-users

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/postgis-users/attachments/20120425/cac28d65/attachment.html>