We recently traveled to Chicago to attend a press event hosted by LizardTech, the leader in file compression.The purpose of the event was to introduce us to the new, GeoExpress 8 and MrSID 4 (MG4)
My colleague, Marc Cheves (co-founder/Managing Editor of the American Surveyor Magazine) had this to say about GeoExpress... Any of you who deal with aerial images have probably encountered the company's popular MrSID file format. It's easy to grasp how the also-popular zip format operates: repeating pixels in an image—for instance, blue pixels in the sky—are replaced by a marker. Then, when the file is uncompressed for viewing, the marker replaces these pixels.
LizardTech's MrSID, however, takes compression to another level. An outgrowth of early-90s research at Los Alamos National Lab, the company has been around for more than a decade, and announced its fourth-generation MG4 (MrSID Generation 4) format at the press event. To deal with non-raster 3D data, the company also handles LiDAR data, either aerial or terrestrial. Because file sizes for aerial or LiDAR data can be enormous, without compression disk space can quickly be exhausted.
Image compression is either lossless or lossy. The former doesn't reduce the original file-size, but the latter actually discards pixels. Using a technique called wavelet compression, the company has figured out a way to dramatically compress images without affecting what the human eye can detect. If you are interested in learning more, the company has issued a 261Kb PDF white paper HERE [PDF file]. Look for a future article in the American Surveyor agazine about this fascinating technology. (Source: Marc Cheves, American Surveyor)
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