I have a few ECW tiles that I want to combine and save as 8 bit unsigned TIF. Together, they're about 180 MB. When I use mosaic to new raster, the resulting TIF ends up being a whopping 1.8GB big. Is ECW simply a far more efficient file format or is there a way to get a comparably sized TIF?

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    LZW is redusing file size typically by 30%. With ECW user can select the compression ratio and 1:20 works usually well for aerial photos etc. So your numbers are not surprising. Create jpeg compressed tiff for getting about same file size. – user30184 Jul 26 '17 at 14:28
  • I ran a few experiments, I guess that is the right answer. If you can change the comment to an answer I'll mark it correct. – MapEngine Jul 26 '17 at 14:42
  • Instead of reinterpolating this nasty compression with a different nasty compression algorithm (further degrading the actual imagery) you should try to just create a mosaic dataset with leaving the images in place. You used to be able to do it in ArcGIS using "Raster Mosaic Dataset" (seems like they removed this tool) .. you could still do it with GDAL and create a vrt. You can't deal with ECW files directly without a license, but you can make a virtual mosaic of some sort and minimize the degradation to the image. – Mike Jul 26 '17 at 17:33

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