Thursday, December 18, 2014

What is the ISIS 3 cube format

ISIS 3 Cube Format - http://isis.astrogeology.usgs.gov/ or Wikipedia

Overview: ISIS (Integrated Software for Imaging Spectrometers) is a generalized software system that has been designed to optimize cartographic and scientific processing of images in planetary datasets. ISIS versions 2 and version 3 both have their own format called an ISIS cube which contains a label area and a data area. The label describes the data and uses a "keyword=value" text format. The label is normally embedded at the top of the file, but ISIS also supports "detached" labels where the label and image block are divided into separate files.

The data area is a 3-dimensional image with axis: samples, lines, and bands. Typically, the sample and line dimensions are used to represent spatial information while the band dimension represents spectral information. Pixels can be stored in 8-bit unsigned integer, 16-bit signed integer, or 32-bit floating-point format. When cubes are created in ISIS3, unless specifically specified, the file will be written using tiles (blocks of pixels). Tiles can be variable in size as defined in the label. In addition to valid numerical pixel values, five types of "special" pixel values are supported: null, high/low instrument saturation, and high/low representation saturation.

Type
Description
8bit Unsigned
16bit Signed
32bit Floating-Point
Null
Pixel has no data available
0
-32768
\xFF\x7F\xFF\xFB (-3.4028226550889044521e+38)
Lis
Pixel lower bound was saturated on the instrument
0
-32767
\xFF\x7F\xFF\xFC
His
Pixel higher bound was saturated on the instrument
0
-32766
\xFF\x7F\xFF\xFD
Lrs
Pixel lower bound was saturated during processing
255
-32765
\xFF\x7F\xFF\xFE
Hrs
Pixel higher bound was saturated during processing
255
-32764
\xFF\x7F\xFF\xFF

Applications with read support for ISIS 3 cubes
  1. IsisDlm (ISIS IDL Interface Documentation) - http://www.astro.cornell.edu/~carcich/LRO/doc/html/main.html 
  2. Geospatial Data Abstraction Library (GDAL). http://www.gdal.org/, http://www.gdal.org/frmt_isis3.html 
  3.  Davinci (AZ State University) - http://davinci.asu.edu/index.php?title=ISIS3_I/O 

Simple command-line GDAL Conversion examples 
Examples:
$  gdal_translate –of GTiff input_32bit.cub output_32bit.tif
$  gdal_translate –of GTiff input_16bit.cub output_16bit.tif
$  gdal_translate –of GTiff input_8bit.cub output_8bit.tif
$  gdal_translate –of Jpeg –ot Byte –scale input.cub output_8bit.jpg
$  gdal_translate –of PNG –ot Byte –scale input.cub output_8bit.png





Figure 1. Illustration of an ISIS image cube, showing the three dimensions of an Isis image: width (samples), height (lines), and depth (bands).