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  1. #1
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    Default oziexplorer can't display 100k USGS geotiff map

    hi,

    i downloaded 100k scale topo map from usgs website for washington DC area:
    [Only registered and activated users can see links. ]

    but i found i'm not able to open the .tiff file in ozi explorer. all i have is a black background on the canvas. however, if i downloaded the same area map in jpg format, oz opens and displays the map just fine. I'm using ver 3.95.6f registered copy of oz.

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  3. #2
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    Hello erdos
    I use JPG files all the time, but am not sure if TIFF and GEOTIFF are the same bar the geotiff having embedded geo co-ords, but the only pre cal map that will load direct is .ECW the rest you need to import and cal.
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    thanks for the reply!


    I've downloaded several 24k topo geotiff maps from USGS website, they all display fine in ozi. for the same area, the geotiff formatted file is 4 times bigger than .jpg format, it also displays smoother. I intended to calibrate both scales of maps for my local area (W. DC) with ozi and use on my phone. it surprises me that ozi can open 24k tiff file but not 100k , just wondering whether I miss something here or it's a limitation of the software.

  5. #4
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    To be honest I don't know, have always used jpg up to about 50MB as I convert from PDF "from my local depart of Minerals and Energy" as I get scaled 250k maps of mining Tenements and then process them to a nice clean JPG and then reduce file size " for pc Ozi " then convert to Ozfx4 for OziCE.
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  6. #5
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    as I suspected, this turned out to be a limitation of ozi software. ozi explorer only support color depth up to 8 bit(256 colors), while USGS 100K topo geotiff maps are available in 24 bit color, I can open USGS 24k topo in ozi since they still use 8 bit color on these older maps.

    from [Only registered and activated users can see links. ],

    The TIFF files supported must have at least the following format :
    •Scanlines must be arranged in strips (not tiles), preferably 1 scanline per strip.
    •256 colors or 256 GrayScale (8 bit) , 16 color (4 bit) , 2 color (B&W)(1 bit) - 16 bit and 24 bit color are not supported.
    •Packbits is the only compression method supported for color images, FAX CCITT 3 can be used for 1 bit (B&W) images.

  7. #6
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    I have no doubt that Global Mapper could easily convert those GeoTiff files to 8bit colour format.
    It has performed faultlessly on other 24bit images for me in the past.

 

 

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