Archiving and distribution of 2-D geophysical data using image formats with lossless compression

Certain types of two-dimensional (2-D) numerical remote sensing data can be losslessly and compactly compressed for archiving and distribution using standardized image formats. One common method for archiving and distributing data involves compressing data files using file compression utilities such as gzip and bzip2, which are widely available on UNIX and Linux operating systems. GZIP-compressed files and bzip2-compressed files must first be uncompressed before they can be read by a scientific application (e.g., MATLAB, IDL). Data stored using an image format, on the other hand, can be read directly by a scientific application supporting that format and, therefore, can be stored in compressed form, saving disk space. Moreover, wide use of image formats by data providers and wide support by scientific applications can reduce the need for providers of geophysical data to develop and maintain software customized for each type of dataset and reduce the need for users to develop and maintain or download and install such software. This letter demonstrates the utility of standardized image formats for losslessly compressing, archiving, and distributing 2-D geophysical data by comparing them with the traditional file compression utilities gzip and bzip2 on several types of remote sensing data. The formats studied include TIFF, PNG, lossless JPEG, JPEG-LS, and JPEG2000. PNG and TIFF are widely supported. JPEG2000 and JPEG-LS could become widely supported in the future. It is demonstrated that when the appropriate image format is selected, the compression ratios can be comparable to or better than those resulting from the use of file compression utilities. In particular, PNG, JPEG-LS, and JPEG2000 show promise for the types of data studied.