A single mapping dataset, or "bigimage" for short, is held in a single directory. The directory contains a small text file called "header" which contains the number of lanes in the bigimage, the width of a single lane in pixels, the height of the image in pixels, and the datatype of the pixel data.
Valid data types are
I2D I2S I4D I4S R4D R4S
Where I and R refer to integer and real, the number is the number of bytes per pixel, and D and S refer to DEC and Sun byte ordering and floating-point type. The lanes are numbered from 1 upwards, and are held in C-style binary files called l1, l2, l3 etc.
An example header file is
nlanes 24 lwidth 1280 lheight 30720 dtype I2D
This means that the directory contains 24 files of pixel data named l1 to l24. Each pixel is represented by a 2-byte integer in DEC format. Each lane is 1280 pixels wide and 30720 pixels high. The values for the pixels are simply written following one another. The two bytes representing the first pixel of the second row follow immediately after the two bytes representing the last pixel of the first row. The files are suitable for reading either using unformatted FORTRAN direct-access reads or by using standard C functions.