RGB-NDVI colour composites for visualizing forest change dynamics

Abstract

A simple and logical technique was developed to display and quantify forest change using three dates of satellite imagery. The normalized difference vegetation index (NDVI) was computed for each date of imagery to define high and low vegetation biomass. Colour composites were generated by combining each date of NDVI with either the red, green, or blue (RGB) image planes in an image display monitor. Additive colour logic was used to interpret forest change (forest harvest and regeneration) across the landscape on the three dale NDVI colour composite. Harvest and regeneration area were quantified by applying a modified parallelepiped classification creating an RGB-NDVI image with 27 classes that were grouped into nine major forest change categories. Road construction, harvest and regeneration status on old clearcuts can be monitored by interpretation of the additive colour observed at any site. Aerial photographs and stand history maps obtained from a major forest industrial landowner were compared with the forest changes indicated by the RGB-NDVI image. The utility of the RGB-NDVI technique for supporting forest inventories and updating forest resource information systems are presented and discussed.