From c559bc0b852094eec3d1e718683c860e65c5b1a1 Mon Sep 17 00:00:00 2001 From: Regina Obe Date: Thu, 15 Dec 2011 02:14:28 +0000 Subject: [PATCH] correct regular_blocking definition, add descriptions for raster_overview columns git-svn-id: http://svn.osgeo.org/postgis/trunk@8426 b70326c6-7e19-0410-871a-916f4a2858ee --- doc/using_raster_dataman.xml | 44 ++++++++++++++++++++++++++++++++---- 1 file changed, 39 insertions(+), 5 deletions(-) diff --git a/doc/using_raster_dataman.xml b/doc/using_raster_dataman.xml index 1c0b4100e..c84417a6f 100644 --- a/doc/using_raster_dataman.xml +++ b/doc/using_raster_dataman.xml @@ -252,7 +252,7 @@ psql -d gisdb -f elev.sql r_table_name raster table - r_raster_column the table that is of type raster. There is nothing in PostGIS preventing you from having multiple raster columns per table so its possible to have a raster table listed multiple times with a different raster column for each. + r_raster_column the column in the r_table_name table that is of type raster. There is nothing in PostGIS preventing you from having multiple raster columns per table so its possible to have a raster table listed multiple times with a different raster column for each. srid The spatial reference identifier of the raster. Should be an entry in the . @@ -273,7 +273,7 @@ psql -d gisdb -f elev.sql same_alignment A boolean that is true if all the raster tiles have the same alignment . Refer to for more details. - regular_blocking This is a true/false constraint flag set on the table to denote if the tiles form a complete rectangle. It is not really validated but just taken as a given. + regular_blocking This is a true/false constraint flag set on the table to denote that the tiles do not overlap, are of the same alignment, pixel size, srid etc. It is not really validated but just taken as a given so should be used for informational. In the future we plan to properly constrain this so that this inforamtion is guaranteed to be right when it returns true num_bands The number of bands in each tile of your raster set. This is the same information as what is provided by @@ -292,11 +292,45 @@ 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 of being a lower resolution caricature of a higher resolution table. These are generated along-side the main raster table when you use the -l switch in raster loading. + Overview tables contain the same constraints as other raster tables as well as additional informational only constraints specific to overviews. + The informaiton in raster_overviews does not duplicate the information in raster_columns. IF you need the information about an overview table present in raster_columns you can join the raster_overviews and raster_columns vuews together to get the full set of information you need. Two main reasons for overviews are: - + Low resolution representation of the core tables commonly used for fast mapping zoom-out. - Computations are generally faster to do on them than their higher resolution parents because there are fewer records and each pixel covers more territory. Though the computations are not as accurate as the high-res tables they support, they can be suitable in many rule-of-thumb computations. - + Computations are generally faster to do on them than their higher resolution parents because there are fewer records and each pixel covers more territory. Though the computations are not as accurate as the high-res tables they support, they can be sufficient in many rule-of-thumb computations. + + + The raster_overviews catalog contains the following columns of information. + + + o_table_catalog The database the overview table is in. This will always reads the current database. + + + o_table_schema The database schema the overview raster table belongs to. + + + o_table_name raster overview table name + + + o_raster_column the raster column in the overview table. + + + + r_table_catalog The database the raster table that this overview services is in. This will always read the current database. + + + r_table_schema The database schema the raster table that this overview services belongs to. + + + r_table_name raster table that this overview services. + + + r_raster_column the raster column that this overview column services. + + + overview_factor - this is the pyramid level of the overview table. The higher the number the lower the resolution of the table. + + -- 2.40.0