[GRASS-user] Re: [GRASS-dev] gdal import an nodata cells

[Michael Perdue]

Ops... Looks like Geotiff does allow for storing no-data values. But  
HFA (not too sure which format IMA is) and others don't appear too.

Question?

is float(nan) equal to double(nan)? If not, does gdal_translate  
understand this when it converts a file stored as float64 to float32?  
gdal_translate allows one to define what the no-data value is, but  
how do I tell it to change the input no-data value to a different  
output no-data value? IE, the no-data value in my surfer file is a  
double precision nan, but I want the no-data value in my output  
GeoTiff (float32) to be -32767. -a_nodata changes the header no-data  
definition but does not change the values of the pixels that  
represent no-data.

Sorry, It's not really a grass question but I thought I'd ask since  
were on the topic and it's currently giving me headaches.

Cheers,

Mike


On 19-Jul-07, at 7:45 PM, Michael Perdue wrote:

>
> gdalinfo will show the nodata value if the file format supports  
> storing the value in the header. So, for surfer, DTED, USGSDEM and  
> such it indicates what the nodata value is but not for GeoTiff, IMA  
> and such.
>
>
>>
>> does gdalinfo show the nodata value? (I'm not sure if it should or  
>> not)
>
> Mike
>
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