From ae47ce85637f55d14a9259d69fc1e73f808487b2 Mon Sep 17 00:00:00 2001 From: Regina Obe Date: Thu, 15 Dec 2011 01:54:12 +0000 Subject: [PATCH] Start raster_overviews section git-svn-id: http://svn.osgeo.org/postgis/trunk@8424 b70326c6-7e19-0410-871a-916f4a2858ee --- doc/using_raster_dataman.xml | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/doc/using_raster_dataman.xml b/doc/using_raster_dataman.xml index 95c2846f9..7c51ee415 100644 --- a/doc/using_raster_dataman.xml +++ b/doc/using_raster_dataman.xml @@ -235,6 +235,7 @@ psql -d gisdb -f elev.sql + Raster Columns Catalog The raster_columns is a catalog of all columns in the table taht are of type raster. It is a view utilizing the constraints on the tables so the information is always consistent even if you restore one raster table from a backup of another database. The following columns exist in the raster_columns catalog. If you created your tables not with the loader or forgot to specified the -C flag during load, you can enforce the constraints after the @@ -288,5 +289,14 @@ psql -d gisdb -f elev.sql + + Raster Overviews + raster_overviews catalogs information about raster table columns used for overviews and additional information about them that is useful to know when utilizing overviews. Overview tables are cataloged in both raster_columns and raster_overviews because they are rasters in their own right but also serve an additional special purpose. These are generated along-side the main raster table when you use the -l switch in raster loading. + Two main reasons for overviews are: + + Low resolution representation of the core tables common used for fast mapping zoom-out. + Computations are faster to do on them though the computations are not as accurate as the high-res tables, they can be suitable in many rule-of-thumb computations. + + -- 2.40.0