[Proj] File Format Translation

[Ames, Kieran J.]

Hello list,
I'd appreciate some guidance on translating MrSID files to geotiffs.
Using gdal_translate, I can convert a MrSID file to geotiff. However,
the resulting file size is on the order of 15 times larger (a 4MB .sid
file becomes a 62MB .tif file).
gdalinfo tells me that the files dimensions and other attributes are the
same. However, I see the following differences that make me wonder if I
can reduce file size.
 
The .sid file:
Band 1 Block=1024x128 Type=Byte, ColorInterp=Gray
  Minimum=59.000, Maximum=189.000, Mean=119.865, StdDev=17.205
  Overviews: 4000x4000, 2000x2000, 1000x1000, 500x500, 250x250, 125x125,
63x63,32x32
 
the resulting .tif file after gdal_translate:
Band 1 Block=8000x1 Type=Byte, ColorInterp=Gray
 
Is there any information here that tells me about gdal_translate
options/switches that may be available to me to make the .tif files
smaller?
 
I have .tif files from other geographies that support viewing reasonably
clear information that are of sizes of about 150KB. I'm guessing that
the MrSID files contain much more information than I'd need in order to
reasonable present the data in a useful form.
 
As background info (FWIW), the mrSID files are utilized in a SmallWorld
app and we'd like to make this raster info available in other
applications. We have no MrSID server in house and, with my limited
knowledge, I am trying to make these rasters available to this new app
as tiffs (since the other area's tiffs seem to work quite well) at no
cost other than my time and my available disk space.
 
Thanks for any suggestions.
 
Kieran
 
 


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