I also as you see tried to divide on 3600 as that was the possible number
of pixel count per geometry polygon (foo2.gid).
Andreas
2011/12/19 Andreas Forø Tollefsen
> Thanks Tom,
>
> I tried to select WHERE (ss).count > 0 and (ss).sum > 0, but i still got
> the same error. I assume that this is
Thanks Tom,
I tried to select WHERE (ss).count > 0 and (ss).sum > 0, but i still got
the same error. I assume that this is something that need to be changed in
the script.
I will do some more testing.
Does anyone have an idea for something that could bypass this in my query?
SELECT foo2.gid, (ss
Yes, well found.
I'm not familiar with plpgsql, but I'm sure it's easy to include some
conditional statement. Just check the postgres documentation.
You can also check if you can put the conditional into your SQL query
(something like 'WHERE count(rast) > 0') so that you don't feed empty
raste
Divisions by zero shouldn't happen as far as I know, at most it should
give you null data as return.
Sounds like a bug.
Perhaps you can check:
http://trac.osgeo.org/postgis/browser/trunk/raster/scripts/plpgsql/st_summarystatsagg.sql
at line 69 it says: "($1).sum / ($1).count"
my guess is that t
Line 59 to 77 in the st_summarystatsagg.sql.
Could it be that line 69: ($1).sum / ($1).count leads to division by zero
error if ($1).count is 0?
How could i change this so this is not the case?
-- raster_summarystatsfinal
-- Final function used by the ST_SummaryStatsAgg aggregate
CREATE OR REPLACE
Updated to latest trunk, and now it works.
However, I ran into a new "division by zero" error. This halts the query.
Could it be that something is divided by integer rather than decimal in the
query, or what else causes this:
ERROR: division by zero
CONTEXT: PL/pgSQL function "raster_summarystat
Andreas,
If you got the latest ST_Clip from the repository, I found this
information with it:
"Addition of C-based ST_MinPossibleValue to replace the existing
ST_MinPossibleVal which uses hard-coded values. Updated dependent
functions and scripts/plpgsql to use new function. Deleted
scripts
Hi Tom,
I tried both functions. The St_AreaWeightedSummaryStats() works great, but
it takes a lot of time to complete.
However, the ST_Clip() i cannot manage to get working. Seems like something
is broken. Any idea what can cause this error?
I installed the latest ST_SummaryStatsAgg() and ST_Clip
Andreas,
I didn't have time to reproduce your problem yet. Did you have any
succes by yourself on this issue?
Could it have something to do with counting the non-data values as
value? This is what I experience with a similar function (ST_Clip) that
consequently gave me the value '0' instead of
On Sun, Dec 4, 2011 at 11:09 AM, Tom van Tilburg
wrote:
> Pierre,
>
> I just ran a test to see the difference between my old method and your new
> method with ST_Clip and ST_SummaryStatsAgg and came up with the following:
>
> 1. The old way took 38 secs. whereas the new one 46 (100 polygons, usual
Pierre,
I just ran a test to see the difference between my old method and your
new method with ST_Clip and ST_SummaryStatsAgg and came up with the
following:
1. The old way took 38 secs. whereas the new one 46 (100 polygons,
usually covering part of 1 raster tile).
2. ST_Clip appears to fill
sers Discussion
> Subject: Re: [postgis-users] Raster pixel value
>
> Pierre, are these two new functions available in the latest trunk revision?
>
> Andreas
___
postgis-users mailing list
postgis-users@postgis.refractions.net
http://postgis.re
Tollefsen
> Sent: Friday, December 02, 2011 8:21 AM
> To: PostGIS Users Discussion
> Subject: Re: [postgis-users] Raster pixel value
>
> Pierre, are these two new functions available in the latest trunk revision?
>
> Andreas
___
post
Pierre, are these two new functions available in the latest trunk revision?
Andreas
___
postgis-users mailing list
postgis-users@postgis.refractions.net
http://postgis.refractions.net/mailman/listinfo/postgis-users
This is great! Fantastic. I will do some testing.
2011/12/1 Tom van Tilburg
> Pierre,
>
> This is great you're working on this. It is exactly what I think that
> pgraster is going to make a great tool.
>
> Last days I didn't really have time to check out things, hopefully this
> week.
>
> Cheers
: postgis-users@postgis.refractions.net
> Subject: Re: [postgis-users] Raster pixel value
>
> Pierre,
>
> This is great you're working on this. It is exactly what I think that
> pgraster is
> going to make a great tool.
>
> Last days I didn't reall
Pierre,
This is great you're working on this. It is exactly what I think that
pgraster is going to make a great tool.
Last days I didn't really have time to check out things, hopefully this
week.
Cheers,
Tom
On 30-11-2011 19:19, Pierre Racine wrote:
Andreas, Tom,
I have put two new func
Andreas, Tom,
I have put two new functions you might be interested by in
http://trac.osgeo.org/postgis/browser/trunk/raster/scripts/plpgsql
The first one, st_areaweightedsummarystats.sql, is usefull when you want to
compute summary stats (like the weighted mean) of values coming from a raster
2011 5:14 AM
> To: PostGIS Users Discussion
> Subject: [postgis-users] Raster pixel value
>
> Hi,
>
> I am trying to calculate the average pixel value in a elevation raster inside
> quadrate polygons.
> However, I am not getting the correct values from my query:
>
&g
Update:
I think my suspicion is correct. If I do a ST_Summarystats().sum and divide
this on 36 my MAX value will be 1.
Hence, I think the number of values counted and the number of observations
counted is not equal.
New query:
DROP TABLE IF EXISTS mountain_phil_cell;
SELECT
a.gid As gid,
(ST_Sum
A small note regarding this issue.
My problem is that I never get a mean value of 1 even if all pixels inside
the geometry is one.
Could this be because: 6x6 pixels goes into one polygon when visually
controlling. If each pixel has the value 1, then this will be calculated as
36 / 36 = 1. However
Could this have to do with the tiling of the raster?
I will try to run the same query with a untiled mountain raster to see if
that changes anything.
Btw. When loading a tiled postgis raster into qgis it shows up with many
artifacts and no data areas. The same raster untiled does not show up the
s
Hi,
Thanks for all of the suggestions. I will do some more testing. However, as
for suggestion 1 i think the pixel size should be the same as the original
raster or am I wrong?
Both the mean_mnt_bin raster and the priogrid_land shapefile can be
downloaded as zip (2 mb) here:
http://gisintersect.c
Andreas,
Would it be possible to share code and/or sample data?
With me St_SummaryStats seems to work correct, even when I set all my
raster values to 1.
Chrs,
Tom
On 24-11-2011 13:42, Andreas Forø Tollefsen wrote:
I double checked the values that I get from this query and they do not
seem t
I know. RTFM before asking dumb questions. Set the ST_Summary(rast, false)
so it does not exclude_nodata_value? Right?
Andreas
2011/11/24 Andreas Forø Tollefsen
> Great. I updated to latest rev and added the st_union.sql to my function
> list. Now it works.
> However, I need to ask one more que
Great. I updated to latest rev and added the st_union.sql to my function
list. Now it works.
However, I need to ask one more question.
When running the script, it calculates the average pixel value inside the
polygon. It does not take into account the NULL DATA values.
Is there any way i can make t
Yes, I think so.
Current windows build is *r8221
*
Also, I think ST_Union(raster) (which I used in the example) is not
included in this version yet.
You would have to download a prototype from.
http://trac.osgeo.org/postgis/browser/trunk/raster/scripts/plpgsql/st_union.sql
Chrs,
Tom
On 24-11-
Great, Thank you so much for this.
However, I do not seem to have the ST_MapAlgebraExpr(rast, rast.)
function. Was this implemented in rev 8001?
Andreas
2011/11/24 Tom van Tilburg
> Andreas,
>
> We did approx. the same thing for non-quadrate polygons. Perhaps it might
> be useful:
>
> Step
Andreas,
We did approx. the same thing for non-quadrate polygons. Perhaps it
might be useful:
Step 1: Make a raster from every polygon, based on the grid
specifications of the elevation raster. Here is also the solution: the
raster cells will only be created for cells that have their midpoin
Hi,
I am trying to calculate the average pixel value in a elevation raster
inside quadrate polygons.
However, I am not getting the correct values from my query:
SELECT gid, AVG(((foo.geomval).val)) as avgmnt
FROM (SELECT p.gid, ST_Intersection(p.cell, r.rast) AS geomval FROM
mountain r, priogrid_
30 matches
Mail list logo
