ACCURACIES IN MAPPING SECONDARY TROPICAL FOREST AGE FROM SEQUENTIAL SATELLITE IMAGERY

Multitemporal satellite images have been used to differentiate, measur e the areal extent of, and determine transitional probabilities among different secondary forest age classes in the tropics. In these studie s, temporal gaps in the satellite archive are common doe to difficulti es associated with availability of cloud-free data, costs, temporal di scontinuities between satellite sensors, etc. In this probability stud y, examples of multitemporal image sequences with data gaps are consid ered in order to illustrate error rates associated with estimating the age of secondary tropical forest. Results indicate that on the order of 8-32% of scene pixels may be misclassified with respect to age of l and cover transitions which occur within the data gap(s) are ignored. Using secondary forest regeneration rates from the literature, calcula tions showed that these gap errors caused the above-ground biomass to be over-estimated by 8-23%. the error rates are scene-dependent. The r esults are presented to flag a potentially significant source of error . (C) Elsevier Science Inc., 1998.