[gdal-dev] What decides zoom-levels

[Per Ohlson]

Ah, so zoom levels are already in the geotiff. I thought they were based on resolution.
That was by the way the whole gdalinfo I printed, so I guess the one who made the tiff hasn't added zoom levels?

Regards
/Per



Per Ohlson, M.Sc. E.E.
Nanight AB - http://www.nanight.se
Stockholm/Gothenburg, Sweden
per.ohlson at nanight-tech.com

On 21 jan 2013, at 20:20, Even Rouault <even.rouault at mines-paris.org> wrote:

> Le lundi 21 janvier 2013 20:15:42, Per Ohlson a écrit :
>> Hi,
>> I have two different geotiff-charts which have the same number of pixels,
>> and similar information when viewing in gdalinfo, but one misbehaves while
>> tiling.
>> For the problem chart, only the zoom levels 0-6 are tiled, but for the
>> correctly handled chart, zoom levels 4-11 are tiled. Both are around
>> 23000x15000 pixels and 72 dpi.
>> So, what decides the zoom levels? I thought it was pixels and dpi..
> 
> You probably don't give the whole context. From the gdalinfo output, I can 
> tell that none of your geotiffs are tiled, or have overviews (precomputed zoom 
> levels). So this may depend on the application that make use of them.
> 
>> 
>> gdalinfo on the working chart gives:
>> 
>> Coordinate System is:
>> Size is 15108, 23181
>> GEOGCS["WGS 84",
>>    DATUM["WGS_1984",
>>        SPHEROID["WGS 84",6378137,298.257223563,
>>            AUTHORITY["EPSG","7030"]],
>>        AUTHORITY["EPSG","6326"]],
>>    PRIMEM["Greenwich",0],
>>    UNIT["degree",0.0174532925199433],
>>    AUTHORITY["EPSG","4326"]]
>> Origin = (167.635052101782918,-27.435225354710909)
>> Pixel Size = (0.000619744987014,-0.000517525434692)
>> Metadata:
>>  AREA_OR_POINT=Area
>> Image Structure Metadata:
>>  COMPRESSION=LZW
>>  INTERLEAVE=PIXEL
>> Corner Coordinates:
>> Upper Left  ( 167.6350521, -27.4352254) (167d38' 6.19"E, 27d26' 6.81"S)
>> Lower Left  ( 167.6350521, -39.4319825) (167d38' 6.19"E, 39d25'55.14"S)
>> Upper Right ( 176.9981594, -27.4352254) (176d59'53.37"E, 27d26' 6.81"S)
>> Lower Right ( 176.9981594, -39.4319825) (176d59'53.37"E, 39d25'55.14"S)
>> Center      ( 172.3166057, -33.4336039) (172d18'59.78"E, 33d26' 0.97"S)
>> Band 1 Block=15108x1 Type=Byte, ColorInterp=Red
>>  Mask Flags: PER_DATASET ALPHA
>> Band 2 Block=15108x1 Type=Byte, ColorInterp=Green
>>  Mask Flags: PER_DATASET ALPHA
>> Band 3 Block=15108x1 Type=Byte, ColorInterp=Blue
>>  Mask Flags: PER_DATASET ALPHA
>> Band 4 Block=15108x1 Type=Byte, ColorInterp=Alpha
>> 
>> gdalinfo on the problem chart gives:
>> Size is 15319, 23593
>> Coordinate System is:
>> GEOGCS["WGS 84",
>>    DATUM["WGS_1984",
>>        SPHEROID["WGS 84",6378137,298.257223563,
>>            AUTHORITY["EPSG","7030"]],
>>        AUTHORITY["EPSG","6326"]],
>>    PRIMEM["Greenwich",0],
>>    UNIT["degree",0.0174532925199433],
>>    AUTHORITY["EPSG","4326"]]
>> Origin = (176.502369113268770,-25.635284667174400)
>> Pixel Size = (0.000619910224237,-0.000526829594898)
>> Metadata:
>>  AREA_OR_POINT=Area
>> Image Structure Metadata:
>>  COMPRESSION=LZW
>>  INTERLEAVE=PIXEL
>> Corner Coordinates:
>> Upper Left  ( 176.5023691, -25.6352847) (176d30' 8.53"E, 25d38' 7.02"S)
>> Lower Left  ( 176.5023691, -38.0647753) (176d30' 8.53"E, 38d 3'53.19"S)
>> Upper Right (     185.999,     -25.635) (185d59'55.59"E, 25d38' 7.02"S)
>> Lower Right (     185.999,     -38.065) (185d59'55.59"E, 38d 3'53.19"S)
>> Center      (     181.251,     -31.850) (181d15' 2.06"E, 31d51' 0.11"S)
>> Band 1 Block=15319x1 Type=Byte, ColorInterp=Red
>>  Mask Flags: PER_DATASET ALPHA
>> Band 2 Block=15319x1 Type=Byte, ColorInterp=Green
>>  Mask Flags: PER_DATASET ALPHA
>> Band 3 Block=15319x1 Type=Byte, ColorInterp=Blue
>>  Mask Flags: PER_DATASET ALPHA
>> Band 4 Block=15319x1 Type=Byte, ColorInterp=Alpha
>> 
>> Regards
>> /Per
>> 
>> 
>> 
>> Per Ohlson, M.Sc. E.E.
>> Nanight AB - http://www.nanight.se
>> Stockholm/Gothenburg, Sweden
>> per.ohlson at nanight-tech.com

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