Changes between Version 26 and Version 27 of WKTRasterTutorial01

Timestamp:

06/11/10 08:39:37 (15 years ago)

Author:

pracine

Comment:

--

WKTRasterTutorial01

@@ -94 +94 @@
 The -r option indicate the series of raster we want to load in the database. You can use *, ?, and character ranges expressed with [] like in a Unix shell to match as many rasters as you wish.
 
-The -t option specify the table in which we want to load them.
-
-Similar to shp2pgsql.exe, the -s option is required to specify the spatial reference system ID. In this case the raster are in "WGS 84" having the SRID number 4326. Unlike some GIS software, PostGIS does not support on the fly reprojection so that we cannot do operations on table stored in different spatial reference systems. As we could see, the caribou point layer was in the projected spatial reference system NAD 83/Quebec Lambert", when the SRTM images are in the geographic spatial reference system "WGS 84". We will have to deal with this later.
-
-The last -k option specify the size of the tiles we want to load in PostGIS.
+The -t option specify the table in which we want to load the raster coverage.
+
+Similar to shp2pgsql.exe, the -s option is required to specify the spatial reference system ID. In this case the raster are in "WGS 84" having the SRID number 4326. Unlike some GIS software, PostGIS does not support on the fly reprojection so that we cannot do operations on table stored with different spatial reference systems. As we could see, the caribou point layer was in "NAD 83/Quebec Lambert" and the SRTM images are in "WGS 84". We will have to deal with this problem later.
+
+The -k option specify the size of the tiles we want to load in PostGIS. Every input raster will be splitted into 100x100 tiles. This dimension is a good compromise allowing efficient raster/vector analysis. It is better if the size of the tiles is a divider of size of each raster. Otherwise the last colomns and rows of tiles from each raster will be filled with nodata values. This might have an impact on performance but not on the result since WKT Raster analysis functions ignore nodata values.
 
 The -I option tells the loader to create a spatial index on the raster tile table. If you forget to add this option you can always add the index by executing a SQL command similar to this one: