Friday, July 10, 2009

ENVI Band Math Tutorial, Help Guide

Looking for the ENVI Band Math tutorial or help guide? Look no more. I found a useful ENVI Band Math tutorial document from ENVI's users guide.

ENVI Band Math is a flexible image processing tool with many capabilities not available in any other image processing system. You can use ENVI's Band Math dialog to define bands or files used as input, to call a user Band Math function, and to write the result to a file or memory. ENVI's Band Math function accesses data spatially by mapping variables to bands or files. Spatial data that are too large to read entirely into memory are automatically accessed using ENVI's data tiling.

I found the document while searching for the right Band Math expression for the different data types and their casting functions. Here are few of them: data type, casting function, dynamic range.

Byte: byte() : - 0 to 255

Integer: fix() : -32768 to + 32767

Unsigned integer: uint() : 0 to 65535

Long integer: long() : approximately +/– 2 billion

Unsigned long integer: ulong() : 0 to approximately 4 billion

Here is the complete Band Math Function Tutorial