Hello,
I converted a ECW file to a compressed GeoTiff file. I am happy with the performance, but I noticed that the resulting file is significantly larger. The original ecw file is 204MB, while the new Geotiff file is 981MB. Is there any reason why the new file is almost five times as large? What can I do to minimize the file size of an image while still being fast in GeoServer, Mapserver, and ArcGIS?
These are the commands that I ran, which in most part are adopted from the "geoserver on steroids" article:
gdal_translate -CO TILED=YES -CO TFW=YES -CO COMPRESS=JPEG -CO BIGTIFF=YES MNLACQ024021.ecw MNLACQ024021.tif
gdaladdo -r average --config compress_overview JPEG --config photometric_overview YCBCR MNLACQ024021.tif 2 4 8 16 32 64 128 256 512 1024
NOTE: The original ecw file does contain tiles. The file seems fast in ArcGIS, but it is slower in GeoServer and Mapserver.
Thank You
Mark Volz, GISP
GIS Specialist
Hi Marc,
Not much. There’s always a trade-off between size and performance. Small file sizes usually come with high compression, and therefore decompression on the map server end takes some time. ECW files are highly compressed. Conversion to most other formats will increase the file size. Increasing by a factor of 5 is not too bad. I’ve had MrSID files decompress to 25x the size.
To increase speed GeoServer and MapServer, keep your TIF as uncompressed, with internal tiles. Then build statistics and overview layers, which shouldn’t be compressed either. Even if your TIF comes out to be 10 GB, you should get decent performance. If you have the space, don’t worry about compression. If you need smaller file sizes, and want good performance in desktop GIS and map servers, then maybe using TIF with LZW or PACKBITS compression might be a good tradeoff, althouhg I would think JPEG would be good as well. Maybe keep your TIF as JPEG compressed but uncompress your overviews.
···
John Callahan
Research Scientist
Delaware Geological Survey
University of Delaware
http://www.dgs.udel.edu
john.callahan@anonymised.com
On Wed, Sep 11, 2013 at 12:08 PM, Mark Volz <MarkVolz@anonymised.com> wrote:
Hello,
I converted a ECW file to a compressed GeoTiff file. I am happy with the performance, but I noticed that the resulting file is significantly larger. The original ecw file is 204MB, while the new Geotiff file is 981MB. Is there any reason why the new file is almost five times as large? What can I do to minimize the file size of an image while still being fast in GeoServer, Mapserver, and ArcGIS?
These are the commands that I ran, which in most part are adopted from the “geoserver on steroids” article:
gdal_translate -CO TILED=YES -CO TFW=YES -CO COMPRESS=JPEG -CO BIGTIFF=YES MNLACQ024021.ecw MNLACQ024021.tif
gdaladdo -r average --config compress_overview JPEG --config photometric_overview YCBCR MNLACQ024021.tif 2 4 8 16 32 64 128 256 512 1024
NOTE: The original ecw file does contain tiles. The file seems fast in ArcGIS, but it is slower in GeoServer and Mapserver.
Thank You
Mark Volz, GISP
GIS Specialist
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