<br><tt><font size=2>>Thanks for the reference Doug. What you suggest
does sound like it could<br>
>work, the only thing is that <br>
>I would need to have this output as a Raster as I am then looking to
use it<br>
>with two other rasters <br>
>to do a weighted combination of them e.g. [rast1 * 0.2] + [rast2 *
0.5] +<br>
?[rast3 * 0.3].<br>
<br>
>Do you know how if I could easily rasterise the output of what you've<br>
>suggested?<br>
</font></tt>
<br><tt><font size=2>James,</font></tt>
<br><tt><font size=2>Unfortunately, I have not waded into rasters inside
postgis yet. I'm speculating that you could generate a raster from
the point values you generated from the suggested calculation. (
Using St_AsRaster, </font></tt><a href=http://postgis.refractions.net/docs/RT_ST_AsRaster.html><tt><font size=2>http://postgis.refractions.net/docs/RT_ST_AsRaster.html
?) </font></tt></a>
<br>
<br><tt><font size=2>For raster algebra, I usually use GRASS r.mapcalculator
- </font></tt><a href=http://grass.fbk.eu/gdp/html_grass64/r.mapcalculator.html><tt><font size=2>http://grass.fbk.eu/gdp/html_grass64/r.mapcalculator.html.
If you can dump your images out to files, you could import them to
grass ( or use r.external to link to them) and perform the calculation
you described. If you want to stay in postgis, just do the calculation
in two steps. </font></tt></a>
<br><tt><font size=2><br>
>Only reason is I'm working on it for a dissertation project and I've
left<br>
>myself little time left to consider this.</font></tt>
<br><font size=2 face="sans-serif">Sounds like my grad school experience
:-)</font>
<br>
<br><font size=2 face="sans-serif">Doug</font>
<br>
<br>
<br><font size=2 face="sans-serif">Doug Newcomb
<br>
USFWS<br>
Raleigh, NC<br>
919-856-4520 ext. 14 doug_newcomb@fws.gov<br>
---------------------------------------------------------------------------------------------------------<br>
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.</font>
<br>
<br>
<br>
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<tr valign=top>
<td width=40%><font size=1 face="sans-serif"><b>JamesH <james.holmes@newcastle.ac.uk></b>
</font>
<br><font size=1 face="sans-serif">Sent by: postgis-users-bounces@postgis.refractions.net</font>
<p><font size=1 face="sans-serif">04/25/2012 02:49 PM</font>
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<td bgcolor=white>
<div align=center><font size=1 face="sans-serif">Please respond to<br>
PostGIS Users Discussion <postgis-users@postgis.refractions.net></font></div></table>
<br>
<td width=59%>
<table width=100%>
<tr valign=top>
<td>
<div align=right><font size=1 face="sans-serif">To</font></div>
<td><font size=1 face="sans-serif">postgis-users@postgis.refractions.net</font>
<tr valign=top>
<td>
<div align=right><font size=1 face="sans-serif">cc</font></div>
<td>
<tr valign=top>
<td>
<div align=right><font size=1 face="sans-serif">Subject</font></div>
<td><font size=1 face="sans-serif">Re: [postgis-users] Simple Point Density
Surface</font></table>
<br>
<table>
<tr valign=top>
<td>
<td></table>
<br></table>
<br>
<br>
<br><tt><font size=2>"Why not convert the raster cell centers to points
, do a query on the <br>
point layer for a square centered on the raster derived point whose
<br>
dimensions are given by the number of tiles in your neighborhood. return
<br>
the number of points divided by the area of the square. ( neighborhoods
<br>
are usually odd numbers of cells, 3x3, 5x5, etc so you have an equal <br>
number around the center cell)"<br>
<br>
Thanks for the reference Doug. What you suggest does sound like it could<br>
work, the only thing is that <br>
I would need to have this output as a Raster as I am then looking to use
it<br>
with two other rasters <br>
to do a weighted combination of them e.g. [rast1 * 0.2] + [rast2 * 0.5]
+<br>
[rast3 * 0.3].<br>
<br>
Do you know how if I could easily rasterise the output of what you've<br>
suggested?<br>
<br>
Only reason is I'm working on it for a dissertation project and I've left<br>
myself little time left to consider this.<br>
<br>
Kind Regards,<br>
James <br>
<br>
<br>
-----<br>
GIS Undergraduate<br>
--<br>
View this message in context: </font></tt><a href="http://postgis.17.n6.nabble.com/Simple-Point-Density-Surface-tp4917343p4917632.html"><tt><font size=2>http://postgis.17.n6.nabble.com/Simple-Point-Density-Surface-tp4917343p4917632.html<br>
Sent from the PostGIS - User mailing list archive at Nabble.com.<br>
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