[OSGeo-Discuss] Open File Formats and Proprietary Algorithms

Landon Blake lblake at ksninc.com
Thu Aug 20 13:22:47 PDT 2009



The imagery I am talking about is from the USDA APFO:



This FAQ contains a snippet about the format:



In an interesting turn of events I note that as of 2008, the USDA is
releasing the county mosaics in JP2 format, not in MRSID. I am not sure
what brought about this change, and I wasn't aware that it had been
made. The same web page indicates that there is a shapefile index for
the individual image tiles.


It appears that you can also download the county mosaics online.


A lot of this has changed (improved) in the last couple of years. I'm
glad I checked again. That being said, the principles from our
discussion still apply. :]



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From: discuss-bounces at lists.osgeo.org
[mailto:discuss-bounces at lists.osgeo.org] On Behalf Of Eric Wolf
Sent: Thursday, August 20, 2009 1:15 PM
To: OSGeo Discussions
Subject: Re: [OSGeo-Discuss] Open File Formats and Proprietary


The MRSID format is a very special case - and perhaps an opportunity for
a new FOSS file format. MRSID is a lossless, fractal-based, multi-scale
raster compression format. LizardTech has the algorithms to encode and
decode MRSID locked up in copyrights, and I believe, patents. Even
companies like ESRI shell out big bucks to LizardTech to be able to read
and write the MRSID format.


I guess I missed the context of the discussion. Is the government
releasing certain data exclusively in this format? If so, I think the
argument can be made against this practice. The different in compression
between MRSID and gziped TIFFs isn't really that great in this day of
cheap disks and fat pipes.



Eric B. Wolf                    New! 720-334-7734
USGS Geographer
Center of Excellence in GIScience
PhD Student 
CU-Boulder - Geography

On Thu, Aug 20, 2009 at 12:27 PM, Landon Blake <lblake at ksninc.com>

I realized that publishing a spec for a file format like MRSID isn't as
clear cut as I had at first thought. If the MRSID software uses a fancy
top-secret compression/decompression algorithm to move data to and from
the file format knowing only the structure of the format would do no
good. You'd have to release the details of the algorithm as well.


I still don't think proprietary file formats are a good idea for
government data released to the public, but I admit that having a
company like LizardTech publish a spec for something like MRSID is not
necessarily a simple task. No doubt a lot of time and money goes into
developing those algorithms.


This makes me wonder about algorithms used to purposefully encrypt
binary file formats. That is another can of worms. It looks like the
easiest thing to do is to start with a file format that was designed to
be open from the very beginning.





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