Changes between Version 2 and Version 3 of WKTRaster/SpecificationFinal01

Timestamp:

Apr 16, 2009, 8:36:23 AM (15 years ago)

Author:

pracine

Comment:

—

WKTRaster/SpecificationFinal01

@@ -108 +108 @@
 
 ----
+== '''RASTER_COLUMNS Metadata Table''' ==
+
+The following metadata table provides external applications and possibly internal tools the ability to discover tables with raster data, and to learn various information about those datasets. 
+
+|| '''Column Name''' || '''Type''' || '''Constraints''' || '''Comments''' ||
+|| r_table_catalog || character varying(256) || NOT NULL || ||
+|| r_table_schema || character varying(256) || NOT NULL || ||
+|| r_table_name || character varying(256) || NOT NULL || ||
+|| r_column || character varying(256) || NOT NULL || ||
+|| srid || integer || NOT NULL || Use 0 for unknown SRID ||
+|| pixel_types || ARRAY[[=VARCHAR=]] || NOT NULL || an array of pixeltypes, one per band.  The band count is implicit in the size of this array.||
+|| out_db || boolean || NOT NULL || false if internal tiles, true if tiles are references to files outside the database ||
+|| regular_blocking || boolean || NOT NULL || false by default, true if all blocks are equal sized, abutted and non-overlapping, started at top left origin (see below) ||
+|| nodata_values || ARRAY[[=DOUBLE=]] ||  || an array of nodata values, one per band. The entry may be NULL to indicate no nodata values.||
+|| pixelsize_x || double || || width of a pixel in geounits (per SRID) ||
+|| pixelsize_y || double ||  || height of a pixel in geounits (per SRID) ||
+|| blocksize_x || integer ||  || the width of a block in pixels (NULL if irregular) ||
+|| blocksize_y || integer ||  || the height of a block in pixels (NULL if irregular) ||
+|| extent|| GEOMETRY || || a polygon geometry containing all raster tiles, or NULL if predefined bounds are not known.  For "regular_blocking" cases this geometry will be a simple rectangle.  In other cases it might be an irregular polygon. ||
+
+If the regular_blocking field is true a number of restrictions are placed on the raster column that is defined:[[BR]]
+[[BR]]
+ 1. All tiles must have the same size (blocksize_x and blocksize_y). 
+ 1. All tiles must be non-overlapping, and appear on regular block grid.
+ 1. The top left block must start at the top left corner of the extent.
+ 1. The right most column, and bottom row of blocks may have portions that extend beyond the raster extent.  These areas will be assumed to be nodata and not part of the described raster.
+ 1. The extent field must be a simple rectangle (non-rotated). 
+
+It is permissable to for regular_blocking rasters to omit some blocks/tiles (sparse rasters) in which case the missing tiles should be assumed to be all nodata or zero valued.