Changes between Version 65 and Version 66 of WKTRasterTutorial01

Timestamp:

06/17/10 13:15:28 (15 years ago)

Author:

pracine

Comment:

—

WKTRasterTutorial01

@@ -145 +145 @@
 
 {{{
-    SELECT rid, ST_AsBinary(rast::geometry) FROM srtm_tiled;
+    SELECT rid, ST_AsBinary(rast::geometry) 
+    FROM srtm_tiled;
 }}}
 
@@ -153 +154 @@
 
 {{{
-    SELECT ST_AsBinary(ST_Buffer(ST_Union(rast::geometry), 0.000001)) FROM srtm_tiled;
+    SELECT ST_AsBinary(ST_Buffer(ST_Union(rast::geometry), 0.000001)) 
+    FROM srtm_tiled;
 }}}
         
@@ -161 +163 @@
 
 {{{
-    SELECT ST_AsBinary((ST_DumpAsPolygons(rast)).geom), (ST_DumpAsPolygons(rast)).val
+    SELECT ST_AsBinary((ST_DumpAsPolygons(rast)).geom), 
+           (ST_DumpAsPolygons(rast)).val
     FROM srtm_tiled
     WHERE rid=34;
@@ -335 +338 @@
 }}}
         
-This version takes only 17 minutes. Almost half the time spent by the preceding one... This little increase in complexity certainly worths the gain in performance. The size of the tiles has also a major effect here. If we restart the whole process with 60 pixels x 60 pixels tiles (60 is a divider of 6000) the intersection operation takes 9 minutes. 200 pixels x 200 pixels: 47 minutes...
+This version takes only 17 minutes. Almost half the time spent by the preceding one... This little increase in complexity certainly worths the gain in performance. The size of the tiles has also a major effect here. If we restart the whole process with 60 pixels x 60 pixels tiles (60 is a divider of 6000) the intersection operation takes 9 minutes. 200 pixels x 200 pixels: 47 minutes... 30 pixels x 30 pixels: 5 minutes. You choose...
 
 Once again you can visualise the result of the query by doing this query in OpenJUMP (you might have to increase RAM allowed to OpenJUMP by changing "-Xmx256M" to "-Xmx1024M" in "OpenJUMPInstallPath/bin/openjump.bat"):
@@ -354 +357 @@
     CREATE TABLE result01 AS
     SELECT id, 
-           sum(st_area(ST_Transform(the_geom, 32198)) * val) / sum(st_area(ST_Transform(the_geom, 32198))) AS meanelev
+           sum(st_area(ST_Transform(the_geom, 32198)) * val) / 
+           sum(st_area(ST_Transform(the_geom, 32198))) AS meanelev
     FROM caribou_srtm_inter
     GROUP BY id