[gdal-dev] ASCII Rasters and 'null' values in python-gdal

[Frank Warmerdam]

Oz Nahum wrote:
> Hi, Thanks for the answer.
> Ok, I admit the way I presented my first email is a bit confusing.
> But the problem is not with the 'null' values. Rather the problem is 
> with the raster containing the no data values as -9999. This is a no 
> data representation like you said. 
> My problem is that GDAL is converting the last -9999 value to this value 
> 31081.
> raster2.asc and looks like this:
> 
> in text editor:
>     |ncols         6
>     nrows         4
>     xllcorner     3366820.0000019
>     yllcorner     5814589.0300007
>     cellsize      10
>     NODATA_value -9999
>     1 1 1 1 1 1
>     1 1 1 1 1 1
>     1 1 1 1 1 1
>     1 1 1 1 -9999 -9999|
> 
> |in python:     
>  >>> dataset = gdal.Open('raster1.asc', GA_ReadOnly)
>  >>> a = gdal_array.DatasetReadAsArray(dataset)
>  >>> a
> array([[    1,     1,     1,     1,     1,     1],
>        [    1,     1,     1,     1,     1,     1],
>        [    1,     1,     1,     1,     1,     1],
>        [    1,     1,     1,     1, -9999, 31081]], dtype=int16)

Oz,

I'm not seeing this behavior on my system:

 >>> a = gdalnumeric.DatasetReadAsArray(ds)
 >>> print a
[[    1     1     1     1     1     1]
  [    1     1     1     1     1     1]
  [    1     1     1     1     1     1]
  [    1     1     1     1 -9999 -9999]]

I'd suggest filing a ticket on the issue and being very specific
about the operating system platform, and GDAL version you are using.
Also, make sure you zip and attach the grid file in case there is some
issue with missing final newline or something that is having an influence.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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