[gdal-dev] how can a Geotiff occupy three times the disk space of an ASCII Grid?

[G. Allegri]

I've translated the ASCII with gdal_translate and I get a reasanable size,
335 MB.
The other Geotiff was exported with ano
ther software.
My question is what, inside the Geotiff structure, can make them so
different in size when gdalfino reports the same dimensions and cell type?

giovanni


2014-07-05 16:02 GMT+02:00 G. Allegri <giohappy at gmail.com>:

> I've converted a Float32 ASCII Grid of 8861 x 9457 cells to Geotiff (with
> deflate compression, predicor=1).
> The original file was 577 MB, the resulting Geotiff is about 1.897 MB.
>
> Here is gdalinfo run on the ASCII:
>
> Driver: AAIGrid/Arc/Info ASCII Grid
> Files: DTM\dtm.asc
>        DTM\dtm.asc.aux.xml
> Size is 8861, 9457
> Coordinate System is `'
> Origin = (1634712.000000000000000,4904391.000000000000000)
> Pixel Size = (10.000000000000000,-10.000000000000000)
> Corner Coordinates:
> Upper Left  ( 1634712.000, 4904391.000)
> Lower Left  ( 1634712.000, 4809821.000)
> Upper Right ( 1723322.000, 4904391.000)
> Lower Right ( 1723322.000, 4809821.000)
> Center      ( 1679017.000, 4857106.000)
> Band 1 Block=8861x1 Type=Float32, ColorInterp=Undefined
>   Min=5.810 Max=1932.780
>   Minimum=5.810, Maximum=1932.780, Mean=393.467, StdDev=316.141
>   NoData Value=-99
>   Metadata:
>     STATISTICS_MAXIMUM=1932,78
>     STATISTICS_MEAN=393,46740210782
>     STATISTICS_MINIMUM=5,81
>     STATISTICS_STDDEV=316,14065359461
>
> And here the Geotiff:
>
> Driver: GTiff/GeoTIFF
> Files: dtm.tif
> Size is 8861, 9457
> Coordinate System is:
> PROJCS["Monte Mario / Italy zone 1",
>     GEOGCS["Monte Mario",
>         DATUM["Monte_Mario",
>             SPHEROID["International 1924",6378388,297.0000000000014,
>                 AUTHORITY["EPSG","7022"]],
>             AUTHORITY["EPSG","6265"]],
>         PRIMEM["Greenwich",0],
>         UNIT["degree",0.0174532925199433],
>         AUTHORITY["EPSG","4265"]],
>     PROJECTION["Transverse_Mercator"],
>     PARAMETER["latitude_of_origin",0],
>     PARAMETER["central_meridian",9],
>     PARAMETER["scale_factor",0.9996],
>     PARAMETER["false_easting",1500000],
>     PARAMETER["false_northing",0],
>     UNIT["metre",1,
>         AUTHORITY["EPSG","9001"]],
>     AUTHORITY["EPSG","3003"]]
> Origin = (1634712.000000000000000,4904391.000000000000000)
> Pixel Size = (10.000000000000000,-10.000000000000000)
> Metadata:
>   AREA_OR_POINT=Area
> Image Structure Metadata:
>   COMPRESSION=DEFLATE
>   INTERLEAVE=BAND
> Corner Coordinates:
> Upper Left  ( 1634712.000, 4904391.000) ( 10d41'17.17"E, 44d16'46.14"N)
> Lower Left  ( 1634712.000, 4809821.000) ( 10d39'51.33"E, 43d25'42.21"N)
> Upper Right ( 1723322.000, 4904391.000) ( 11d47'50.78"E, 44d15'27.69"N)
> Lower Right ( 1723322.000, 4809821.000) ( 11d45'28.67"E, 43d24'26.04"N)
> Center      ( 1679017.000, 4857106.000) ( 11d13'36.91"E, 43d50'40.36"N)
> Band 1 Block=8861x1 Type=Float64, ColorInterp=Gray
>   NoData Value=-99
>
> giovanni
>
> --
> Giovanni Allegri
> http://about.me/giovanniallegri
> Twitter: https://twitter.com/_giohappy_
> blog: http://blog.spaziogis.it
> GEO+ geomatica in Italia http://bit.ly/GEOplus
>



-- 
Giovanni Allegri
http://about.me/giovanniallegri
Twitter: https://twitter.com/_giohappy_
blog: http://blog.spaziogis.it
GEO+ geomatica in Italia http://bit.ly/GEOplus
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