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List: postgis-users
Subject: Re: [postgis-users] 2 raster map algebra returning all zeros
From: "Nordgren, Bryce L -FS" <bnordgren () fs ! fed ! us>
Date: 2016-03-10 23:17:29
Message-ID: 82E7C9A01FD0764CACDD35D10F5DFB6E8E2230 () 001FSN2MPN1-044 ! 001f ! mgd2 ! msft ! net
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Ahh, forgive stupid question:
ST_Rescale flipped the sign of my y pixel size. Changing to ST_Rescale(rast_750, \
375,-375) makes everything ducky.
Bryce
From: postgis-users [mailto:postgis-users-bounces@lists.osgeo.org] On Behalf Of \
Nordgren, Bryce L -FS
Sent: Thursday, March 10, 2016 12:00 PM
To: PostGIS Users Discussion (postgis-users@lists.osgeo.org) \
<postgis-users@lists.osgeo.org>
Subject: [postgis-users] 2 raster map algebra returning all zeros
I have a table with two raster columns, which I'm trying to combine into a third \
column using the two raster MapAlgebra. The columns represent fire events at \
different resolutions, which fortuitously are a simple factor of two different. These \
are all 8BUI rasters interpreted as Boolean masks (0==False,1==True). The third \
column will eventually represent a logical OR of the two masks, at the higher \
resolution. Each row covers exactly the same extent at the different resolutions. \
Trying an expression which should simply copy from one raster into the result, I get:
select rid, ST_ValueCount(rast_375,1.) as r375,
ST_ValueCount(ST_Rescale(rast_750, 375.), 1.) as r750,
ST_ValueCount(ST_SetBandNoDataValue(ST_MapAlgebra(
rast_375, 1,
ST_Rescale(rast_750, 375.), 1,
'[rast2]',
'8BUI', 'FIRST'),3.),1.) as test
from "Run_0000".fire_events_raster
WHERE rast_375 is not null and rast_750 is not null ORDER BY r375 DESC;
rid | r375 | r750 | test
------+------+------+------
166 | 2448 | 1708 | 0
216 | 1044 | 1020 | 0
916 | 1039 | 2068 | 0
...
Running ST_SameAlignment() on the input rasters returns true across the board. They \
have the same upperleft corner. SRIDS are identical (96630; \
http://spatialreference.org/ref/sr-org/6630/) If I use either input raster as both \
the first and second raster to MapAlgebra, I get output.
Any ideas what could be throwing MapAlgebra off?
Thanks,
Bryce
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<p class="MsoNormal"><span style="color:#1F497D">Ahh, forgive stupid question: <o:p>
</o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">ST_Rescale flipped the sign of my y \
pixel size. Changing to ST_Rescale(rast_750, 375,-375) makes everything \
ducky.<o:p></o:p></span></p> <p class="MsoNormal"><span \
style="color:#1F497D"><o:p> </o:p></span></p> <p class="MsoNormal"><span \
style="color:#1F497D">Bryce<o:p></o:p></span></p> <p class="MsoNormal"><span \
style="color:#1F497D"><o:p> </o:p></span></p> <div>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b>From:</b> postgis-users \
[mailto:postgis-users-bounces@lists.osgeo.org] <b>On Behalf Of </b>Nordgren, Bryce L \
-FS<br> <b>Sent:</b> Thursday, March 10, 2016 12:00 PM<br>
<b>To:</b> PostGIS Users Discussion (postgis-users@lists.osgeo.org) \
<postgis-users@lists.osgeo.org><br> <b>Subject:</b> [postgis-users] 2 raster \
map algebra returning all zeros<o:p></o:p></p> </div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I have a table with two raster columns, which I’m trying \
to combine into a third column using the two raster MapAlgebra. The columns represent \
fire events at different resolutions, which fortuitously are a simple factor of two \
different. These are all 8BUI rasters interpreted as Boolean masks \
(0==False,1==True). The third column will eventually represent a logical OR of the \
two masks, at the higher resolution. Each row covers exactly the same extent at the \
different resolutions. Trying an expression which should simply copy from one raster \
into the result, I get: <o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">select rid, \
ST_ValueCount(rast_375,1.) as r375, <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier \
New""> ST_ValueCount(ST_Rescale(rast_750, \
375.), 1.) as r750,<o:p></o:p></span></p> <p class="MsoNormal"><span \
style="font-family:"Courier \
New""> \
ST_ValueCount(ST_SetBandNoDataValue(ST_MapAlgebra(<o:p></o:p></span></p> <p \
class="MsoNormal"><span style="font-family:"Courier \
New""> &nb \
sp; \
rast_375, 1, <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier \
New""> &nb \
sp; ST_Rescale(rast_750, \
375.), 1, <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier \
New""> &nb \
sp; '[rast2]',
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier \
New""> &nb \
sp; '8BUI', \
'FIRST'),3.),1.) as test <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">from \
"Run_0000".fire_events_raster <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">WHERE rast_375 \
is not null and rast_750 is not null ORDER BY r375 DESC;<o:p></o:p></span></p> <p \
class="MsoNormal"><o:p> </o:p></p> <p class="MsoNormal"><span \
style="font-family:"Courier New"">rid | r375 | r750 | \
test<o:p></o:p></span></p> <p class="MsoNormal"><span \
style="font-family:"Courier \
New"">------+------+------+------<o:p></o:p></span></p> <p \
class="MsoNormal"><span style="font-family:"Courier New""> 166 | 2448 \
| 1708 | 0<o:p></o:p></span></p> <p class="MsoNormal"><span \
style="font-family:"Courier New""> 216 | 1044 | 1020 \
| 0<o:p></o:p></span></p> <p class="MsoNormal"><span \
style="font-family:"Courier New""> 916 | 1039 | 2068 \
| 0<o:p></o:p></span></p> <p \
class="MsoNormal">…<o:p></o:p></p> <p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Running ST_SameAlignment() on the input rasters returns true \
across the board. They have the same upperleft corner. SRIDS are identical \
(96630; <a href="http://spatialreference.org/ref/sr-org/6630/">http://spatialreference.org/ref/sr-org/6630/</a>) \
If I use either input raster as both the first and second raster to MapAlgebra, I get \
output. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Any ideas what could be throwing MapAlgebra off? <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks,<o:p></o:p></p>
<p class="MsoNormal">Bryce<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New \
Roman",serif"><br> <br>
<br>
<br>
This electronic message contains information generated by the USDA solely for the \
intended recipients. Any unauthorized interception of this message or the use or \
disclosure of the information it contains may violate the law and subject the \
violator to civil or criminal penalties. If you believe you have received this \
message in error, please notify the sender and delete the email immediately. \
<o:p></o:p></span></p> </div>
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