[FWTools] gdal merge file size

Adam Yesaitis adamy at wtgroupllc.com
Tue Jan 6 15:31:40 EST 2009

Hello Jeff,

Thank you for your response.  This method seems like it would work. 
However, one issue is that my images do not match up perfectly edge to edge 
(some overlap others due to registration).  The pnmcat command does not take 
this into consideration.  It will just place them edge to edge. Does anyone 
have an idea as to how I could accomplish this while maintaining the 
worldfile data throughout the process?

Thanks again,

Adam Yesaitis
Western Technologies Group
Tel: 908-725-1143
Fax: 908-725-1488
E-mail: adamy at wtgroupllc.com
----- Original Message ----- 
From: "Jeff Ruby" <jgr007 at gmail.com>
To: "Adam Yesaitis" <adamy at wtgroupllc.com>
Cc: <fwtools at lists.maptools.org>
Sent: Monday, December 29, 2008 3:50 PM
Subject: Re: [FWTools] gdal merge file size

> Hi Adam,
> One of the quickest methods I've found for operations like this is to:
> - use djpeg convert the images to pnm
> - use pnmcat to concatenate images in the same row
> - use pnmcat again to concatenate the rows
> - use gdal_translate to convert the pnm to an unregistered tiff
> - rename .jgw for upper left to appropriate .tfw
> At that point you have a registered tif and you can use gdal_translate
> to convert it to any image GDAL supports.
> This method is a little clunky, but it's pretty fast.  If the image is
> small enough you may be able to convert the pnm directly to jpg using
> cjpeg.
> If you're using Windows djpeg/cjpeg and pnmcat all work well through
> cygwin for this purpose.  I've used it to create tiffs that are on the
> order of 100GB.
> If anyone has another method, I'd love to hear it.
> Cheers!
> -Jeff
> On Mon, Dec 29, 2008 at 2:45 PM, Adam Yesaitis <adamy at wtgroupllc.com> 
> wrote:
>> Hello,
>>     I am attempting to use the gdal_merge utility to mosaic 
>> pre-registered
>> aerial photographs and provide a worldfile for the output.  I am using 
>> RGB
>> satellite images in .JPG format averaging about 7MB per image.  The 
>> problem
>> is that my output file size for say 10 images is extremely large ( 5.9
>> GB).  Also it takes a very long tome for the utility to complete with 
>> only
>> 10 maps.  Is there anything I can do to drastically reduce the size of my
>> output to better reflect the initial input sizes or any way I can speed 
>> the
>> process up?  Any thoughts would be greatly appreciated.
>> Adam Yesaitis
>> Western Technologies Group
>> Tel: 908-725-1143
>> Fax: 908-725-1488
>> E-mail: adamy at wtgroupllc.com
>> _______________________________________________
>> FWTools mailing list
>> FWTools at lists.maptools.org
>> http://lists.maptools.org/mailman/listinfo/fwtools
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