Changes between Initial Version and Version 1 of Ticket #3230


Ignore:
Timestamp:
Mar 16, 2010, 1:46:02 PM (14 years ago)
Author:
warmerdam
Comment:

This is really a GDAL issue, and likely ought to be filed there.

The code referenced is for missing blocks which are returned as zeros. There does not seem to be any other nodata handling in the driver so I'm not sure what is returned for blocks with a mixture of data and nodata. I suspect there needs to be broader nodata support in the driver and that the missing blocks should be handled like the rest of it.

I am cc:ing Howard who wrote the SDE driver though I'm not sure if he is in a position to work on it any more.

I will note that one approach to nodata that does not require setting aside specific "nodata" values is to support nodata masks per GDAL RFC 15:

​http://trac.osgeo.org/gdal/wiki/rfc15_nodatabitmask

It would be nice if MapServer supported these masks when available.

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  • Ticket #3230

    • Property Cc hobu added
    • Property Priority high → normal

  • Ticket #3230 – Description

    initial v1  
    22
    33using the SDE raster layers we get trouble because of the handling of missing values(NODATA):
    4 
     4{{{
    55        // ArcSDE says the block has no data in it.
    66        // Write 0's and be done with it
    7 
     7}}}
    88While working with classified rasters we are able to avoid a 0 (null) class. But more often we are processing signed float data with 0 as a valid value. Setting nodata values to 0 gives illegal values in the data stream.
    99
    … …  
    1818
    1919The following expression in a mapfile using raster data should then be interpreted correctly by gdal:
    20 
     20{{{
    2121        class
    2222                name "nodata"
    … …  
    2424                color   255 255 255
    2525        end
     26}}}