[gdal-dev] Fwd: MBTiles Write support

Mon Apr 18 06:35:44 PDT 2016

Hi all,
I recently tested the MBTiles write support in the latest beta with good
results.
I'm now testing it with larger files, so here is some of my comments and
questions.

Version is: GDAL 2.1.0beta1, released 2016/04/01
The gdalinfo of the input file is:

Driver: GTiff/GeoTIFF
Files: mosaic.tif
Size is 645661, 308112
Coordinate System is:
PROJCS["Monte Mario / Italy zone 1",
    GEOGCS["Monte Mario",
        DATUM["Monte_Mario",
            SPHEROID["International 1924",6378388,297,
                AUTHORITY["EPSG","7022"]],
            TOWGS84[-104.1,-49.1,-9.9,0.971,-2.917,0.714,-11.68],
            AUTHORITY["EPSG","6265"]],
        PRIMEM["Greenwich",0,
            AUTHORITY["EPSG","8901"]],
        UNIT["degree",0.0174532925199433,
            AUTHORITY["EPSG","9122"]],
        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"]],
    AXIS["X",EAST],
    AXIS["Y",NORTH],
    AUTHORITY["EPSG","3003"]]
Origin = (1473060.112236728700000,4930249.736560207800000)
Pixel Size = (0.055042625523929,-0.055042631056927)
Metadata:
  AREA_OR_POINT=Area
Image Structure Metadata:
  COMPRESSION=CCITTFAX4
  INTERLEAVE=BAND
Corner Coordinates:
Upper Left  ( 1473060.112, 4930249.737) (  8d39'39.60"E, 44d31'27.30"N)
Lower Left  ( 1473060.112, 4913290.441) (  8d39'42.77"E, 44d22'17.68"N)
Upper Right ( 1508598.989, 4930249.737) (  9d 6'29.55"E, 44d31'28.93"N)
Lower Right ( 1508598.989, 4913290.441) (  9d 6'28.53"E, 44d22'19.29"N)
Center      ( 1490829.551, 4921770.089) (  8d53' 5.11"E, 44d26'54.09"N)
Band 1 Block=256x256 Type=Byte, ColorInterp=Palette
  NoData Value=1
  Image Structure Metadata:
    NBITS=1
  Color Table (RGB with 2 entries)
    0: 0,0,0,255
    1: 255,255,255,0

The command I used is:

\>gdal_translate mosaic.tif full_def9.mbtiles -of MBTILES -expand rgb -co
TILE_FORMAT=PNG8 -co ZLEVEL=9
Input file size is 645661, 308112
0...10...20...30...40...50...60...70...80ERROR 1: Failure when inserting
partial tile (row=759306,col=1099566) at zoom_level=21 : database or disk
is full
ERROR 1: full_def9.mbtiles, band 4: An error occurred while writing a dirty
block
ERROR 1: Failure when inserting partial tile (row=759306,col=1099566) at
zoom_level=21 : database disk image is malformed
ERROR 1: Failure when inserting partial tile (row=759306,col=1099566) at
zoom_level=21 : database disk image is malformed
ERROR 1: Failure when inserting partial tile (row=759306,col=1099566) at
zoom_level=21 : database disk image is malformed
ERROR 1: Failure when inserting partial tile (row=759306,col=1099576) at
zoom_level=21 : database disk image is malformed

NOTE: without the "-expand rgb" option, all the output tiles will be black,
gdal_translate will warn you.

The process failed due to insufficient disk space (70Gb free was not
enough) but the resulting incomplete file (7Gb) looks good.
Most of the space was used by the "partial_tiles" database, is there any
settings I can use to force a more frequent "flush" of the tiles in the
main database?

The file was created with zoom level = 21, that is more than we need, so I
tried to use ZOOM_LEVEL_STRATEGY to generate a level 20.
My plan was to generate a level 20 file with gdal_translate and then add
the level 19 with gdaladdo but both ZOOM_LEVEL_STRATEGY=UPPER and
ZOOM_LEVEL_STRATEGY=LOWER seems to compute the same zoom level 21.
How is the zoom level computed?

Thank you

Regards
Lorenzo Pini
Software Engineer

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