DISCRIMINATION OF ADELGID-DAMAGE ON SINGLE BALSAM FIR TREES WITH AERIAL REMOTE-SENSING DATA

Compact Airborne Spectrographic Imager (CASI) multi-spectral and panch romatic images were acquired in July 1992 over two forest plots infest ed by the balsam woolly adelgid (Adelges piceae) in western Newfoundla nd. A panchromatic image (pixel size approximately 25 cm) was used as a georeference for the coarser resolution multi-spectral data which we re resampled to 1m and 0.5 m, then carefully tied to a detailed plot p lan showing the locations of 159 trees. Field observations for each of these trees included a ranking for adelgid damage class according to a standard Forest Insect and Disease Survey (FIDS) scheme. A discrimin ant analysis of the multi-spectral CASI imagery (together with semi-va riance parameters and texture derivations) indicated that damage cause d by the balsam woolly adelgid on balsam fir (Abies balsamea) trees co uld be detected and separated into severity classes with a range of ac curacy between 40-76 per cent depending on the classification scheme a nd the type of remote sensing variables available to perform discrimin ation. The 'best' discriminant results obtained were based on a single pixel sample extracted from a 0.5 m multi-spectral image comprised of six bands centred on 454, 550, 590, 662, 836, and 895 nm. A central t heme of this continuing effort is that the combination of multi-spectr al, spatial and high spectral resolution image processing may provide further insight into optimal damage detection-and subsquent hazard rat ings-using digital remote sensing imagery.