847 
beetle infestation with an accuracy of 91 percent 
using 1:3000 scale photographs. Encouraging 
results have also been given in another report 
(Murtha, 1985) in which colour infrared large-scale 
photography (1:2000) was used to help distinguish 
between healthy and unattacked Engelmann spruce 
(Picea englemannii Parry). 
The objective of this study was to differentiate 
between green attacked and unattacked trees using 
imagery acquired with an airborne MEIS (Multi 
element Electro-optical Imaging Sensor). 
A previous study showed that MEIS data at 1.4-m 
resolution was sufficient to permit the detection of 
more trees with the appearance of red attack than 
3.4-m resolution MEIS imagery and conventional 
aerial photography (Kneppeck and Ahern 1989), 
emphasizing the need for data with high resolution. 
2. STUDY AREA 
The area chosen for the Investigation is located 
approximately 35 km southeast of Cranbrook, British 
Columbia near latitude 49° 23’ N, longitude 115° 17’ 
W in the Elk Forest. The terrain is fairly flat with 
elevations ranging from 823 m to 884 m above sea 
level. During the site selection process several 
areas containing red attacked trees were monitored 
during the summer months for signs of beetle 
spread to adjacent trees. Image data was then 
acquired over those areas exhibiting extensive 
green attack (symptoms, as mentioned earlier, 
included pitch tubes and boring dust found near 
the base of trees). Trees under attack were mainly 
lodgepole pine. Other species, not attacked by the 
mountain pine beetle, were black cottonwood 
(Populus trichocarpa Torr. & Gray), white spruce 
(Picea glauca (Moench) Voss), western larch (Larix 
occidentalis Nutt.), and douglas fir (Pseudotsuga 
menziesii (Mirb.) Franco). 
3. DATA ACQUISITION 
Four lines of MEIS data were acquired on high- 
density tape September 1, 1989 from 579 m, 1539 m, 
and 3414 m above ground level. The corresponding 
instantaneous field of view was 0.4 m, 1.0 m, and 
2.2 m, respectively. The MEIS data consisted of a 
blue band (448 nm), a green band (549 nm), a red 
band (676 nm) and five infrared bands (711, 722, 
735, 751, and 875 nm). The minimum and maximum 
limits of each band are provided in Table 1. These 
bands closely resembled those determined by Ahern 
(1988) to have potential for detecting mountain pine 
beetle stress at an early age. Colour infrared aerial 
photography was obtained concurrent with the MEIS 
data. 
The overflight was timed such that it was 
subsequent to the period of beetle spread, which is 
usually from mid to late July. One month following 
the MEIS data acquisition trees were checked on the 
ground for mountain pine beetle green attack. A 
tree was considered at the green attack stage if all 
of the following conditions were met: 
needles were still green 
reddish coloured boring dust was found at the 
base of trees and pitch tubes were formed 
around entrance holes on the bark 
by cutting into the tree with an axe, blue stain 
fungi was found in the sapwood. 
A total of 256 green attacked trees and 250 healthy 
trees were identified in four principal areas which 
we shall refer to as Galloway, Jaffrey, Rosen Lake 
and Elko. Every tree was tagged with a number, 
and its location was marked onto an acetate sheet 
attached to a colour infrared photograph. A record 
was kept of each tree which included its location, 
tag number, and general health and a 35 mm 
photograph of each tree was obtained. 
4. DATA ANALYSIS 
This section reports on the analysis conducted to 
date for the 0.4 m resolution MEIS imagery acquired 
over Jaffrey and Galloway. 
The MEIS data for all lines were copied from high- 
density tape to computer compatible tape. 
Subscenes were made of each of the four areas 
mentioned earlier and histograms were generated 
for each band. A colour infrared image was made 
using bands corresponding to the infrared (751 
nm), red (676nm), and green (549 nm) portions of 
the spectrum, displayed as blue, green and red 
respectively. The data were linearly contrast 
stretched before display. 
Training areas were made for 156 trees whose 
locations had been marked on the colour infrared 
photographs. The training area for each tree 
included only fully sunlit pixels, and excluded 
shadowed or partially shadowed pixels. Statistics 
extracted for each tree included the mean digital 
signal level for each band. Table 2 provides a 
summary of the number of attacked and unattacked 
trees used in the analysis. For each tree the mean 
digital signal level per band was transferred into 
the RS/1 statistical package. 
It was apparent from the data that the digital signal 
level (DSL) of attacked and unattacked trees was 
generally highest in the 711 nm band. To reduce 
variations caused by differing illumination between 
trees, the DSL of each band was divided by the DSL 
of the 711 nm band for every tree. Using this 
normalized data, the average DSL for the attacked 
and unattacked trees was calculated. Figures 1 and 
2 show the average DSLs of attacked and 
unattacked trees in Jaffrey and Galloway 
respectively. The standard deviations of the DSLs 
for each band were also calculated and displayed on 
Figures 1 and 2 as the average of the standard 
deviation for the attacked trees and the unattacked 
trees. 
Figures 1 and 2 show that there are noticeable 
differences between attacked and unattacked 
lodgepole pines at both sites. However, the 
differences in digital signal level between the two 
sites are larger than the differences between 
attacked and unattacked trees within a single site. 
While the Galloway trees generally exhibit a spectral 
shape which is typical for healthy green vegetation 
(see Ahern, 1988 for samples of foliar spectra of 
attacked and unattacked lodgepole pine), the 
Jaffrey trees have higher visible wavelength 
Intensities and lower near infrared intensities than 
one would expect. This difference between the 
Galloway trees and the Jaffrey trees is also visible 
on the colour infrared photography acquired during 
the mission: the Jaffrey trees have, in general, an 
appearance which is more gray and less pink than 
the Galloway trees. These differences suggest a 
lower level of vegetation vigour for the Jaffrey 
sample, which may be related to different growing 
conditions. 
Additionally, the differences between attacked and 
unattacked trees are generally smaller than the 
standard deviation of an individual measurement.