[GRASS5] floating AI ASCII GRID import
Maciek Sieczka
werchowyna at pf.pl
Sat Nov 27 15:51:55 EST 2004
From: "Frank Warmerdam" <fwarmerdam at gmail.com>
>> The value range should be:
>> min=176.945400
>> max=284.015600
>>
>> And it is the case when 'r.in.arc type=DCELL' is used for importing.
>>
>> However, if 'r.in.gdal' or 'r.in.arc type=FCELL' is used then:
>>
>> min=176.945404
>> max=284.015594
>>
>> I suppose there should be no difference. What is the reason?
> Well, the obvious conclusion is that a FCELL, which I presume reads as a
> 4byte float gives
> slightly less precision than DCELL which is an 8byte float. The change
> in the seventh digit would seem to be what we would expect from floating
> point precision limitations.
Ok, so why doesn't r.in.gdal recognize what precission the input requires?
Actually, all floating point AI ASCII GRIDs I met were DCELL, no matter
where they came from. So maybe the default for the r.in.gdal in case of the
AI ASCII GRID should be DCELL instead of FCELL?
GRASS DEVELOPERS - I couldn't find a GUI entry for the 'r.in.arc' in the
File->Import->Raster. Shouldn't it be there?
Maciek
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