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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Osahon,<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><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo1'><![if !supportLists]><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><span style='mso-list:Ignore'>1)<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>The overview factors do not have to be factors of 2.<o:p></o:p></span></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo1'><![if !supportLists]><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><span style='mso-list:Ignore'>2)<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>You get fewer rows the higher the factor because the factor gives you lower resolution.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>So if your original number of rows (tiles) = 1000<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><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>An overview factor of 3 = 1000/Power(2,3) = 1000/(2*2*2) = 125 rows<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><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo1'><![if !supportLists]><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><span style='mso-list:Ignore'>3)<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>If you tiled your main raster in 250x250 then all factors have tile sizes 250x250, but the higher rasters are packing more of the original tiles (geometry space) in each tile because they are lower resolution.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>So in the over view factor =2 case – each tile contains 4 tiles of the original raster (but at 1/4 the resolution).<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><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo1'><![if !supportLists]><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><span style='mso-list:Ignore'>4)<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>You get scrap tiles because each tile must maintain the same size but includes more than 1 tile from original, but must contain a whole tile (not a half tile for example)<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>So lets say you had not 1000 tiles but 1001 tiles, that last tile of your over view 3 would have only 1 tile of the original and the remaining 7 slots would be filled in with no data filler<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>so that the tile size of 250x250<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><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><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><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><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><p class=MsoNormal style='margin-left:.5in'><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'> Osahon Oduware [mailto:osahon.gis@gmail.com] <br><b>Sent:</b> Thursday, May 11, 2017 6:37 AM<br><b>To:</b> PostGIS Development Discussion <postgis-devel@lists.osgeo.org>; Regina Obe <lr@pcorp.us>; Pierre Racine <pierre.racine@sbf.ulaval.ca><br><b>Subject:</b> Fwd: [postgis-users] PostGIS Rasters Overview Factor<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p><div><div><p class=MsoNormal style='margin-left:.5in'>Could anyone help with the questions below?<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:12.0pt;margin-left:.5in'>---------- Forwarded message ----------<br>From: <b>Osahon Oduware</b> <<a href="mailto:osahon.gis@gmail.com" target="_blank">osahon.gis@gmail.com</a>><br>Date: Thu, May 11, 2017 at 11:00 AM<br>Subject: Re: [postgis-users] PostGIS Rasters Overview Factor<br>To: PostGIS Users Discussion <<a href="mailto:postgis-users@lists.osgeo.org" target="_blank">postgis-users@lists.osgeo.org</a>><br>Cc: David Haynes <<a href="mailto:haynesd2@gmail.com" target="_blank">haynesd2@gmail.com</a>>, Regina Obe <<a href="mailto:lr@pcorp.us" target="_blank">lr@pcorp.us</a>>, Pierre Racine <<a href="mailto:pierre.racine@sbf.ulaval.ca" target="_blank">pierre.racine@sbf.ulaval.ca</a>><br><br><o:p></o:p></p><div><p class=MsoNormal style='margin-left:.5in'>Hi David,<o:p></o:p></p><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'>Thanks for your response. Sorry, I forgot to mention that I also performed the loading using the tile flag <b>-t 250x250</b> using the syntax below:<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><span style='font-size:9.5pt;color:#500050'>raster2pgsql -s <SRID> -d -Y -e -I -C -F -M -l 2,4,8,16,32,64,128,256,512,1024,2048,4096,8192,16384,32768,65536 /path/to/raster/file </span><o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><span style='font-size:9.5pt;color:#500050'>-t 250x250 <table_name> | psql -h <host_address> -U postgres -p 5432 -d <database></span><o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'>I obtained the quoted information below from this link:<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><a href="http://postgis.net/docs/manual-2.2/using_raster_dataman.html#RT_Raster_Overviews" target="_blank">http://postgis.net/docs/manual-2.2/using_raster_dataman.html#RT_Raster_Overviews</a><o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'>"overview_factor - this is the pyramid level of the overview table. The higher the number the lower the resolution of the table. raster2pgsql if given a folder of images, will compute overview of each image file and load separately. Level 1 is assumed and always the original file. Level 2 is will have each tile represent 4 of the original. So for example if you have a folder of 5000x5000 pixel image files that you chose to chunk 125x125, for each image file your base table will have (5000*5000)/(125*125) records = 1600, your (l=2) o_2 table will have ceiling(1600/Power(2,2)) = 400 rows,<b> your (l=3) o_3 will have ceiling(1600/Power(2,3) ) = 200 rows</b>. If your pixels aren't divisible by the size of your tiles, you'll get some scrap tiles (tiles not completely filled). Note that each overview tile generated by raster2pgsql has the same number of pixels as its parent, but is of a lower resolution where each pixel of it represents (Power(2,overview_factor) pixels of the original)."<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><b>Question 1</b><o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'>The example given in the document above states that "<b>... </b>your (l=2) o_2 table will have ceiling(1600/Power(2,2)) = 400 rows,<b> your (l=3) o_3 will have ceiling(1600/Power(2,3) ) = 200 rows ...." </b>It appears the <b>Power </b>function is being used internally to compute the number of rows for the overview table based on the overview_factor i.e. Power(2,<overview_factor>). If this is the case, <b>does it imply that the factors could be numbers other than power of 2 (e.g. 3 in this case), but cannot be greater than 1,000 ?</b><o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><b>Question 2</b><o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'>After doing a bulk loading of <b>650 raster source files</b> with a tiling option flag, <b>-t 250x250</b>, and overview option flag, <b><span style='font-size:9.5pt;color:#500050'>-l 2,4,8,16,32,64,128,256</span></b> my raster table had <b>1,040,000 rows</b> and the highest factor overview table, o_256_<table_name>, had <b>650 rows, </b>while the lowest factor table, o_2_<table_name>, had <b>260,000 rows.</b><o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'>Going by the example given in the document above, I would expect the opposite of what I am getting i.e. the highest factor overview table with more records (rows) than the lowest factor overview table. <b>What could be responsible for this?</b><o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><b>Question 3</b><o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'>The document above states that "... If your pixels aren't divisible by the size of your tiles, you'll get some scrap tiles (tiles not completely filled) ...."<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'>When I viewed the raster on QGIS (<b>see attached images</b>), I discovered that I get black portions on a large portion of the image when completely zoomed out. I only get to see the raster image when I zoom-in sufficiently (even for black portions).<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><b>What could be responsible for this black portions (see attached images) as my pixels are obviously divisible by the tile size (250x250)?</b><o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'>I would be glad if someone could help out with the above questions.<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div></div><div><div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p><div><p class=MsoNormal style='margin-left:.5in'>On Wed, May 10, 2017 at 5:12 PM, David Haynes <<a href="mailto:haynesd2@gmail.com" target="_blank">haynesd2@gmail.com</a>> wrote:<o:p></o:p></p><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in'><div><p class=MsoNormal style='margin-left:.5in'>You are correct overviews are powers based. Also it does not look like you specified tile size in your raster2pgsql statement<o:p></o:p></p><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><span style='font-size:9.5pt;color:black'>raster2pgsql -s <SRID> -d -Y -e -I -C -F -M -t <pixels> x <pixels> -l 2,4,8,16,32</span><o:p></o:p></p></div></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p><div><div><div><p class=MsoNormal style='margin-left:.5in'>On Wed, May 10, 2017 at 11:04 AM, Osahon Oduware <<a href="mailto:osahon.gis@gmail.com" target="_blank">osahon.gis@gmail.com</a>> wrote:<o:p></o:p></p></div></div><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in'><div><div><div><div><p class=MsoNormal style='margin-left:.5in'>Hi All,<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'>I tried loading a raster with overviews using the raster2pgsql tool using the syntax below:<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'>raster2pgsql -s <SRID> -d -Y -e -I -C -F -M -l 2,4,8,16,32,64,128,256,512,1024,2048,4096,8192,16384,32768,65536 /path/to/raster/file <table_name> | psql -h <host_address> -U postgres -p 5432 -d <database><o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'>but it gave an error message stating that the overview factor cannot be more than 1,000.<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'>I would like to know how the Overview-factor works. Must the value for the Overview-factor be in Powers of 2 (i.e. 2,4,8,16,...)?<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:.5in'>I would be glad if someone could help my understanding.<o:p></o:p></p></div></div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div></div><p class=MsoNormal style='margin-left:.5in'>_______________________________________________<br>postgis-users mailing list<br><a href="mailto:postgis-users@lists.osgeo.org" target="_blank">postgis-users@lists.osgeo.org</a><br><a href="https://lists.osgeo.org/mailman/listinfo/postgis-users" target="_blank">https://lists.osgeo.org/mailman/listinfo/postgis-users</a><o:p></o:p></p></blockquote></div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><p class=MsoNormal style='margin-left:.5in'><br>_______________________________________________<br>postgis-users mailing list<br><a href="mailto:postgis-users@lists.osgeo.org" target="_blank">postgis-users@lists.osgeo.org</a><br><a href="https://lists.osgeo.org/mailman/listinfo/postgis-users" target="_blank">https://lists.osgeo.org/mailman/listinfo/postgis-users</a><o:p></o:p></p></blockquote></div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div></div></div></div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div></div></body></html>