MONITORING FOREST CANOPY ALTERATION AROUND THE WORLD 
WITH DIGITAL ANALYSIS OF LANDSAT IMAGERY 
Lee D. Miller* Darrel L. Williams 
Professor of Forest Science Environmental Physical Scientist 
Texas A&M University NASA/Goddard Space Flight Center 
Abstract 
Sufficient experience has gradually been accumulated to indicate that the greatest potential 
for the sustained applications of Landsat-type imagery by the forestry profession is the mon- 
itoring of areas where forest cover is subject to rapid alteration by either natural or manmade 
activities. Preliminary tests of the hypothesis that forest canopy alteration can be readily 
monitored with digital processing of Landsat MSS data have been completed. A collection of 
small, individual research efforts involving forest sites from around the world are presented 
to illustrate the types of forest canopy monitoring which can be undertaken, the approaches 
available, and the potential results which can be achieved. All of these case studies deal with 
digital analysis of Landsat imagery, but they vary considerably in complexity and types of 
analysis procedures employed. 
Overview 
A substantial portion of the reported applications of satellite remote sensing to forest eco- 
systems has dealt with attempts to identify tree species or forest types.! Sufficient experience 
has gradually been accumulated to indicate that this may not be the most important applica- 
tion of the Landsat-type satellites by the forestry profession. The normal progression of 
events in the application of remote sensing to each new topic area has generally been “to de- 
tect”, then “to identify’’ and finally ''to monitor". Usually the supportive research activity 
has progressed from one plateau to another in this chain, often spending several years at each 
level. Remote sensing research on the applications of satellite imagery to forestry has just 
reached the third plateau (i.e., to monitor") and it promises to be the most fruitful. 
Successional changes in forest land cover generally take 20 to 50 years or more. Airphotos 
and their interpretation have proven quite successful for forest tree species and type inven- 
tories, especially with the increased use of color photographic materials. Since ecological 
succession from one forest type to another forest type occurs over long time-frames of tens 
of years, the existing airphoto-based forest cover mapping programs will continue to be 
“appropriate technology”. It seems unreasonable to assume that a viable, economically justi- 
fiable program for the remote sensing of forest lands from space could be built around making 
measurements at frequencies of once every five or ten years, regardless of how easy or 
*A portion of the work reported upon was completed while serving as a Senior Post-doctoral Research 
Associate of the National Research Council assigned to the Earth Resources Branch at the National Aero- 
nautics and Space Administration’s (NASA) Goddard Space Flight Center. 
IMead, R. A., and Meyer, M. P., 1977. Landsat digital data application to forest vegetation and land-use 
classification in Minnesota. Proc. of the 1977 Machine Processing of Remotely Sensed Data Symposium, 
IEEE Cat. No. 77CH1218-7 MPRSD. LARS, Purdue, Indiana. pp. 270-279.