[GRASS-dev] Re: [GRASS GIS] #73: r.out.gdal tiff output does not work

[Markus Metz]

GRASS GIS wrote:
> #73: r.out.gdal tiff output does not work
> --------------------------+-------------------------------------------------
>   Reporter:  helena       |       Owner:  grass-dev at lists.osgeo.org
>       Type:  defect       |      Status:  new                      
>   Priority:  critical     |   Milestone:  6.4.0                    
>  Component:  Raster       |     Version:  svn-trunk                
> Resolution:               |    Keywords:  r.out.gdal, tiff         
>   Platform:  Unspecified  |         Cpu:  Unspecified              
> --------------------------+-------------------------------------------------
> Comment (by hamish):
>
>  my 2c o'today,
>   
...
>   * exit with an error if user supplied nodata= is outside of range for the
>  given type. if no value is given use the following rules:
>    - signed int types: minimum in range
>    - unsigned int types: maximum in range
>    - all floating point: IEEE's NaN
>   
Problem with NaN? According to IEEE 754, x == y is always FALSE if 
either x or y or both are NaN. Assuming (nodata = 
GDALGetRasterNoDataValue()) == NaN, then going through all cells if 
(cell == nodata) will always be FALSE, nodata cells may not be detected? 
Depends on each implementation of nodata detection? Can be solved for 
GRASS, but how is this done in all other GIS applications?

Markus M