USGS MIPS Ratio Documentation

USGS MIPS Ratio Documentation

This program generates an output image file equal to the ratio of two input image files. A multiplication factor is applied to the ratio results to ensure that they are within a desired DN range(e.g., use 100 to keep the results in 0 to 255 8-bit range).

The equation used is:

           Numerator
Output =  ----------- * Factor
          Denominator

where,

Numerator is a DN value from line X and sample Y from the input 
image being used as the numerator

Denominator is a DN value from the same line X and sample Y as in 
the numerator, but from the image being used as the denominator

and,

Factor is a floating point/real multiplicative coefficient

Files

This program requires two input unsigned 8-bit , or two signed 16-bit , or two 32-bit floating point image files and generates an output image file having the same bit type. The following information is transferred from the input file to the output file(if appropriate):

Image labels
Mosaic labels
Projection labels
Sonar labels
Navigation file
History file

The first input file is always used as the numerator and the second as the denominator images.

Parameters

FACT: This parameter is used as a multiplicative coefficient to keep the ratio results in the desired DN range for the output image's bit type. That is, 0 to 255 for unsigned byte 8-bit images and -32768 to 32768 for signed word images(e.g., FACT = 100 is often a good value to use for 8-bit data).

Uses

Ratioing is a procedure often used with multispectral data. It is useful for several things, including the supression/removing, to a first order, brightness variations due to topography. Thus, the ratio image results often have very little topography information and enhance differences between surface materials/colors(e.g, vegetation, soils, etc). However, topography may still appear in the ratio if additive haze corrections are not applied before ratioing.

Examples

From left to right: Landsat TM Band 4 is the numerator and Landsat TM Band 3 is the denominator; the ratio of Band4 / Band 3 is on the right. Note, the combination of these TM Bands generates a "vegetation ratio" image where the amount/density of vegetation is correlated to the DN/brightnesss(i.e., brighter pixels have more vegetation).

[Example Image]