Changes between Version 41 and Version 42 of WKTRasterTutorial01


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Timestamp:
Jun 11, 2010, 12:16:41 PM (11 years ago)
Author:
pracine
Comment:

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  • WKTRasterTutorial01

    v41 v42  
    142142}}}
    143143       
    144 Vectorizing all the table would be way too long and probably impossible to load in OpenJUMP.
     144Vectorizing all the table would have been way too long and the huge amount of geometry would have benn impossible to load in OpenJUMP (and most GIS software).
    145145
    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.