missing map tiles- not all tiles are dispalyed

[Don]

Kurt Kuo wrote:
> Hi List,
> I have a ka-map application for showing the basic road network. The
> performance of ka-map seems not so stable. Part of tiles are missing
> while zooming in/out. It even shows blank map sometimes. Any idea
> how/why this happens and where to start to solve this problem?
>
> Thanks in advance.
>
> Kurt
>
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i am having a similar problem suing drg USGS topos.  Some quads will
display and others will be blank.  As a test I recreated the index using
gdalt index using just one of the files that was not being displayed.  I
thought there might be a conflict, but it did not display.  gdalinfo on
both files is similar.
One of the following is displayed and the other is not.
Driver: GTiff/GeoTIFF
Size is 4621, 5690
Coordinate System is `'
Origin = (1931528.610000,652223.430000)
Pixel Size = (8.00000000,-8.00000000)
Metadata:
  TIFFTAG_XRESOLUTION=250
  TIFFTAG_YRESOLUTION=250
  TIFFTAG_RESOLUTIONUNIT=2 (pixels/inch)
Corner Coordinates:
Upper Left  ( 1931528.610,  652223.430)
Lower Left  ( 1931528.610,  606703.430)
Upper Right ( 1968496.610,  652223.430)
Lower Right ( 1968496.610,  606703.430)
Center      ( 1950012.610,  629463.430)
Band 1 Block=4621x1 Type=Byte, ColorInterp=Palette
  Color Table (RGB with 256 entries)
    0: 0,0,0,255
    1: 255,255,255,255

Driver: GTiff/GeoTIFF
Size is 4672, 5730
Coordinate System is `'
Origin = (1672707.010000,653706.430000)
Pixel Size = (8.00000000,-8.00000000)
Metadata:
  TIFFTAG_XRESOLUTION=250
  TIFFTAG_YRESOLUTION=250
  TIFFTAG_RESOLUTIONUNIT=2 (pixels/inch)
Corner Coordinates:
Upper Left  ( 1672707.010,  653706.430)
Lower Left  ( 1672707.010,  607866.430)
Upper Right ( 1710083.010,  653706.430)
Lower Right ( 1710083.010,  607866.430)
Center      ( 1691395.010,  630786.430)
Band 1 Block=4672x1 Type=Byte, ColorInterp=Palette
  Color Table (RGB with 256 entries)
    0: 0,0,0,255
    1: 255,255,255,255

The file that did not display has a tfw that is:
8.000
  0.000
  0.000
 -8.000
 1931532.610
  652219.430

the one that does display has tfw file that is:
 8.000
  0.000
  0.000
 -8.000
 1672711.010
  653702.430

I am wondering what is wrong.  I suspect that perhaps one of the tif
files was encoded in an older tiff file format and gdal/mapscript does
not recognize it.  Is there a log file somewhere that would list perhaps
an error message?  Any suggestions?