[Gdal-dev] ArcGrid to IMG conversion: huge file

[Petteri Packalen]

Hi,

More clarification about this IMAGINE nodata issue. IMAGINE prefers the 
term BACKGROUND. It isn't strictly "notada" as we understand the concept. 
Often zero is used as background value but it cannot be defined in 
IMG-file (at least I haven't found such a functionality in 10+ years). 
Many dialogs has an option "Ignore Zero in Stats" which serves a kind of 
surrogate to nodata functionality. Some import dialogs allows user to 
select whether "nodata" is converted to zero or e.g. minimum value of the 
current datatype.

Best regards
Petteri

================================
Petteri Packalén 
University of Joensuu 
Faculty of Forestry 
P.O. Box 111 
80101 Joensuu
Finland 
e-mail: packalen at cs.joensuu.fi 
================================


On Thu, 9 Mar 2006, Thom DeCarlo wrote:

> Markus,
> The IMG format doesn't support the concept of "NODATA", and by default does
> not use compression. It does support ESRI-style run length encoding, but I
> haven't seen it used much. You might do better converting to geotiff which
> supports LZW compression and Frank has extended it to support a NODATA tag.
>
> --
> Thom DeCarlo
> ------------------------------------------------------
>           Experience is a wonderful thing
> It allows you to recognize a mistake when you make it again.
>
>> -----Original Message-----
>> From: Markus Neteler
>> Sent: Thursday, March 09, 2006 6:04 AM
>> To: GDAL-dev list
>> Subject: [Gdal-dev] ArcGrid to IMG conversion: huge file
>>
>> Hi,
>>
>> when converting the
>>   Landscan Global Population 2000 Database
>> from
>>   http://www.fao.org/geonetwork/srv/en/metadata.show?id=1261
>>
> [snip]
>>
>> Apparently the NoData isn't passed to IMG.
>> Is the created IMG file probably uncompressed
>> which leads to this big file size?
>>
>> Best regards
>>
>>  Markus
>>
>
>
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