User's Guide

Compute fractional vegetation index from NDVI image

Function:

FRACTVEG computes a fractional vegetation image from the NDVI (numerical differential vegetation index) derived from AVHRR imagery using thresholds empirically derived by Joe Santanello, PSU. Pixels between the lower threshold (0.06) and the upper threshold (0.60) are assigned fractional vegetation values proportional to the square of the difference between the NDVI value and the lower threshold. Pixels with NDVI values below the lower threshold are assigned a fractional vegeation value of zero; and those above the upper threshold, a value of 100 percent. The fractional vegetation values are rounded to the nearest percent, and stored as BYTE datatype.

Parameters:

IN

Name of input NDVI image.

OUT

Name of output fractional vegetation image.

Examples:

1. LAS> fractveg p04_ndvi p04frveg

   Convert the NDVI image for the fourth period of the year to the corresponding fractional vegetation image.

Description/Algorithm:

Procdure FRACTVEG uses program MAP to perform the actual conversion.

Nonfatal Error Messages:

None.

Fatal Error Messages:

Messages may be generated by program MAP -- see its documentation.