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List: postgis-users
Subject: Re: [postgis-users] raster operations
From: "Regina Obe" <lr () pcorp ! us>
Date: 2018-06-13 17:29:52
Message-ID: 000001d4033c$23b9fea0$6b2dfbe0$ () pcorp ! us
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It doesn't grab adjacent tiles. To consider adjacent tiles you'd need to use \
ST_Union to stitch together multiple tiles.
From: postgis-users [mailto:postgis-users-bounces@lists.osgeo.org] On Behalf Of David \
Haynes
Sent: Wednesday, June 13, 2018 12:56 PM
To: postgis-users@lists.osgeo.org
Subject: [postgis-users] raster operations
I have a question about how to focal operations for raster statistics are working. I \
started off comparing the old depreciated function st_mapalgebrafctngb with the \
current version st_mapalgebra. The difference I have determined is that the \
st_mapalgebrafctngb will pass the call back function to the raster dataset similar to \
the st_mapalgebra, but as the function approaches the edge of the raster tile things \
get wonky. What are values that are assigned to pixels that do not have sufficient \
neighbors? When I run this bit of code. The ST_Value function reports that no values \
have been assigned. I assume this can be remedied by adding information through \
userargs.
with smoothed_raster as
(
SELECT st_mapalgebrafctngb(rast, 1, NULL, 1, 1, 'st_mean4ma(double \
precision[][][],text,text[])'::regprocedure, 'ignore', NULL) as rast
FROM glc2000_clipped_250 r
WHERE r.rid = 25
), original_raster as
(
SELECT r.rast
FROM glc2000_clipped_250 r
WHERE r.rid = 25
)
SELECT x, y, ST_Value(s.rast, x,y) as smoothed, ST_Value(o.rast, x,y) as original
FROM smoothed_raster s, original_raster o
CROSS JOIN generate_series(1,10) as x
CROSS JOIN generate_series(1,10) as y
This leads me to a larger question regarding focal analysis functions for raster \
datasets. Do these functions cross the tiles? Assume you have 9 tiles and each tile \
is composed of 3x3 pixels. Tiles 1-3 in row 1, 4-6 row 2 etc. If you have a \
neighborhood analysis function performing on tile 5. Will it grab adjacent pixels in \
tile 6? Unfortunately the examples I created returned with the same result.
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vlink="#954F72"><div class=WordSection1><p class=MsoNormal><span \
style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>It doesn't \
grab adjacent tiles. To consider adjacent tiles you'd need to use ST_Union to \
stitch together multiple tiles.<o:p></o:p></span></p><p class=MsoNormal><span \
style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><div \
style='border:none;border-left:solid blue 1.5pt;padding:0in 0in 0in 4.0pt'><div><div \
style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p \
class=MsoNormal><b><span \
style='font-size:11.0pt;font-family:"Calibri",sans-serif'>From:</span></b><span \
style='font-size:11.0pt;font-family:"Calibri",sans-serif'> postgis-users \
[mailto:postgis-users-bounces@lists.osgeo.org] <b>On Behalf Of </b>David \
Haynes<br><b>Sent:</b> Wednesday, June 13, 2018 12:56 PM<br><b>To:</b> \
postgis-users@lists.osgeo.org<br><b>Subject:</b> [postgis-users] raster \
operations<o:p></o:p></span></p></div></div><p \
class=MsoNormal><o:p> </o:p></p><div><div><p class=MsoNormal><span \
class=gmail-m2033918191318644142cye-lm-tag><span style='font-size:9.5pt'>I have a \
question about how to focal operations for raster statistics are working. I started \
off comparing the old depreciated function st_mapalgebrafctngb with the current \
version st_mapalgebra. The difference I have determined is that the \
st_mapalgebrafctngb will pass the call back function to the raster dataset similar to \
the st_mapalgebra, but as the function approaches the edge of the raster tile things \
get wonky. What are values that are assigned to pixels that do not have sufficient \
neighbors? When I run this bit of code. The ST_Value function reports that no values \
have been assigned. I assume this can be remedied by adding information through \
userargs.</span></span><span \
style='font-size:9.5pt'><o:p></o:p></span></p></div><div><p class=MsoNormal><span \
style='font-size:9.5pt'><o:p> </o:p></span></p></div><div><p \
class=MsoNormal><span class=gmail-m2033918191318644142cye-lm-tag><span \
style='font-size:9.5pt'>with smoothed_raster as</span></span><span \
style='font-size:9.5pt'><o:p></o:p></span></p></div><div><p class=MsoNormal><span \
class=gmail-m2033918191318644142cye-lm-tag><span \
style='font-size:9.5pt'>(</span></span><span \
style='font-size:9.5pt'><o:p></o:p></span></p></div><div><p class=MsoNormal><span \
class=gmail-m2033918191318644142cye-lm-tag><span style='font-size:9.5pt'>SELECT \
st_mapalgebrafctngb(rast, 1, NULL, 1, 1, 'st_mean4ma(double \
precision[][][],text,text[])'::regprocedure, 'ignore', NULL) as \
rast</span></span><span style='font-size:9.5pt'><o:p></o:p></span></p></div><div><p \
class=MsoNormal><span class=gmail-m2033918191318644142cye-lm-tag><span \
style='font-size:9.5pt'>FROM glc2000_clipped_250 r</span></span><span \
style='font-size:9.5pt'><o:p></o:p></span></p></div><div><p class=MsoNormal><span \
class=gmail-m2033918191318644142cye-lm-tag><span style='font-size:9.5pt'>WHERE r.rid \
= 25</span></span><span style='font-size:9.5pt'><o:p></o:p></span></p></div><div><p \
class=MsoNormal><span class=gmail-m2033918191318644142cye-lm-tag><span \
style='font-size:9.5pt'>), original_raster as</span></span><span \
style='font-size:9.5pt'><o:p></o:p></span></p></div><div><p class=MsoNormal><span \
class=gmail-m2033918191318644142cye-lm-tag><span \
style='font-size:9.5pt'>(</span></span><span \
style='font-size:9.5pt'><o:p></o:p></span></p></div><div><p class=MsoNormal><span \
class=gmail-m2033918191318644142cye-lm-tag><span style='font-size:9.5pt'>SELECT \
r.rast</span></span><span style='font-size:9.5pt'><o:p></o:p></span></p></div><div><p \
class=MsoNormal><span class=gmail-m2033918191318644142cye-lm-tag><span \
style='font-size:9.5pt'>FROM glc2000_clipped_250 r</span></span><span \
style='font-size:9.5pt'><o:p></o:p></span></p></div><div><p class=MsoNormal><span \
class=gmail-m2033918191318644142cye-lm-tag><span style='font-size:9.5pt'>WHERE r.rid \
= 25</span></span><span style='font-size:9.5pt'><o:p></o:p></span></p></div><div><p \
class=MsoNormal><span class=gmail-m2033918191318644142cye-lm-tag><span \
style='font-size:9.5pt'>)</span></span><span \
style='font-size:9.5pt'><o:p></o:p></span></p></div><div><p class=MsoNormal><span \
class=gmail-m2033918191318644142cye-lm-tag><span style='font-size:9.5pt'>SELECT x, y, \
ST_Value(s.rast, x,y) as smoothed, ST_Value(o.rast, x,y) as \
original</span></span><span \
style='font-size:9.5pt'><o:p></o:p></span></p></div><div><p class=MsoNormal><span \
class=gmail-m2033918191318644142cye-lm-tag><span style='font-size:9.5pt'>FROM \
smoothed_raster s, original_raster o</span></span><span \
style='font-size:9.5pt'><o:p></o:p></span></p></div><div><p class=MsoNormal><span \
class=gmail-m2033918191318644142cye-lm-tag><span style='font-size:9.5pt'>CROSS JOIN \
generate_series(1,10) as x</span></span><span \
style='font-size:9.5pt'><o:p></o:p></span></p></div><div><p class=MsoNormal><span \
class=gmail-m2033918191318644142cye-lm-tag><span style='font-size:9.5pt'>CROSS JOIN \
generate_series(1,10) as y</span></span><span \
style='font-size:9.5pt'><o:p></o:p></span></p></div><div><p class=MsoNormal><span \
class=gmail-m2033918191318644142cye-lm-tag><span \
style='font-size:9.5pt'> </span></span><span \
style='font-size:9.5pt'><o:p></o:p></span></p></div><div><p class=MsoNormal><span \
class=gmail-m2033918191318644142cye-lm-tag><span style='font-size:9.5pt'>This leads \
me to a larger question regarding</span></span><span class=cye-lm-tag><span \
style='font-size:9.5pt'> </span></span><span \
class=gmail-m2033918191318644142cye-lm-tag><span style='font-size:9.5pt'>focal \
analysis functions for raster datasets. Do these functions cross the tiles? Assume \
you have 9 tiles and each tile is composed of 3x3 pixels. Tiles 1-3 in row 1, 4-6 row \
2 etc. If you have a neighborhood analysis function performing on tile 5. Will it \
grab adjacent pixels in tile 6? Unfortunately the examples I created returned with \
the same result.</span></span><span \
style='font-size:9.5pt'><o:p></o:p></span></p></div><p \
class=MsoNormal><o:p> </o:p></p></div></div></div></body></html>
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