[gdal-dev] blocksize and overviews

[Ooms Bart]

Hello all,
I have a grid on a 1m resolution with a tilesize of 8000x8000.
To speed up the rendering process I have created overviews with gdaladdo, the result you can see in the gdalinfo below.
The default blocksize is 512x512.
My questing handles the combination of blocksize and overviews. The blocksize is 512x512 and the lowest resolution of the overview generates a block of 63x63. Are the lower resolution overviews usefull? I suppose it is only usefull to create overviews until 500x500 if I have a blocksize of 512x512. Am I right?

[root at -appl bin]# gdalinfo /dsg/data/2d008/01/01/box_524_5689_hist.tiff
Driver: GTiff/GeoTIFF
Files: /dsg/data/2008/01/01/box_524_5689_hist.tiff
Size is 8000, 8000
Coordinate System is:
PROJCS["ETRS89 / UTM zone 31N",
    GEOGCS["ETRS89",
        DATUM["European_Terrestrial_Reference_System_1989",
            SPHEROID["GRS 1980",6378137,298.2572221010002,
                AUTHORITY["EPSG","7019"]],
            TOWGS84[0,0,0,0,0,0,0],
            AUTHORITY["EPSG","6258"]],
        PRIMEM["Greenwich",0],
        UNIT["degree",0.0174532925199433],
        AUTHORITY["EPSG","4258"]],
    PROJECTION["Transverse_Mercator"],
    PARAMETER["latitude_of_origin",0],
    PARAMETER["central_meridian",3],
    PARAMETER["scale_factor",0.9996],
    PARAMETER["false_easting",500000],
    PARAMETER["false_northing",0],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]],
    AUTHORITY["EPSG","25831"]]
Origin = (524000.000000000000000,5696999.000000000000000)
Pixel Size = (1.000000000000000,-1.000000000000000)
Metadata:
  AREA_OR_POINT=Area
Image Structure Metadata:
  COMPRESSION=LZW
  INTERLEAVE=BAND
Corner Coordinates:
Upper Left  (  524000.000, 5696999.000) (  3d20'42.66"E, 51d25'25.28"N)
Lower Left  (  524000.000, 5688999.000) (  3d20'40.71"E, 51d21' 6.32"N)
Upper Right (  532000.000, 5696999.000) (  3d27'36.86"E, 51d25'23.86"N)
Lower Right (  532000.000, 5688999.000) (  3d27'34.27"E, 51d21' 4.90"N)
Center      (  528000.000, 5692999.000) (  3d24' 8.62"E, 51d23'15.14"N)
Band 1 Block=512x512 Type=Int16, ColorInterp=Gray
  NoData Value=10000
  Overviews: 4000x4000, 2000x2000, 1000x1000, 500x500, 250x250, 125x125, 63x63


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