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Posted on January 10th, 2013

Free For All – 7-Zip

Data storage is not free as we all know, and many geospatial files are really large, especially high resolution aerial and satellite imagery. In fact, the minimum size order of 50-cm color WorldView-2 satellite imagery with 16-bit depth has a file size over 500 megabytes (mb)! So then, what is a viable solution for long-term storage?

I am guessing that many of you use the same solution as I do – file compression. If that is the case, you need to give 7-Zip a look. It is a freeware program that does a superb job at compression with a lot of great options to boot. 7-Zip is particularly powerful as it creates .7z files which is claimed to be the file type with the highest compression ratios possible. Even if the claim is not true, .7z format does at least create more compressed files than you will find in ZIP format – perhaps the most common compressed file format. In fact, in our G-FAQ this month, I test the claims made about .7z format on a high resolution TIFF imagery file.

A screengrab of the 7-Zip user interface.

Here is a list of my favorite options that are offered in 7-Zip:

  • Open more than 20 compressed file formats and compress into more than 5 formats, including .7z, .zip and .tar
  • Ability to create password-protected compressed files
  • Support for compressed files split into multiple, smaller volumes
  • Compressed files can be updated with new, uncompressed files
  • Right-click menu support for key compression options in a Windows environment
  • Dual core support to increase compression speeds

You can download the latest and beta versions of 7-Zip here.

Until my next edition of Free For All, happy hunting for free GIS data!

Brock Adam McCarty
Map Wizard
(720) 470-7988

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