Changes between Version 42 and Version 43 of WKTRasterTutorial01


Ignore:
Timestamp:
Jun 11, 2010, 12:18:27 PM (11 years ago)
Author:
pracine
Comment:

--

Legend:

Unmodified
Added
Removed
Modified
  • WKTRasterTutorial01

    v42 v43  
    146146You will notice that a small area in the upper left corner of the vectorized tile is missing. This is an area with nodata value pixels. Any analysis function in PostGIS WKT Raster takes the nodata value into account. This means that those areas will be omitted from the operation. For example in the upcoming intersection operation, if a buffer completely overlaps a nodata value area of one tile, st_intersects(rast, geom) will return false for this tile/buffer couple and st_intersection(rast, geom) will return an "EMPTY GEOMETRY". If the buffer partially overlap a nodata value area and intersect other parts of the tile, st_intersects(rast, geom) will return true for this tile/buffer couple and st_intersection(rast, geom) will only returns parts of the tile with values, omiting parts with nodata values.
    147147
    148 You can verify that your raster has a nodatavalues set and the effective value of the nodata value by doing this query:
     148You can verify that your raster has a nodatavalues set and the effective value of the nodata value by doing this query in pgAdmin III:
    149149
    150150{{{
     
    154154}}}
    155155
    156 I you want a query to ignore the nodata value set and treat it like any other value, you can always replace any rast argument with ST_SetBandHasNodataValue(rast, FALSE) like in this query:
     156If you want a query to ignore the nodata value and treat it like any other value of the raster, you can always replace the rast parameters with ST_SetBandHasNodataValue(rast, FALSE) like in this pgAdmin III query:
    157157
    158158{{{