Section mapped spruce budworm infestation during 
overflights with a helicopter and by means of photo 
interpretation. Four damage classes were mapped 
based on percentage of crown affected: light 
(0-25%), moderate (26-50%), heavy (51-75%) and severe 
(76-100%). 
A spruce budworm infestation is a difficult remote 
sensing detection problem. Damaged spruce needles, 
which turn reddish-brown, may occur on only a portion 
of the tree. Due to the resolution of the sensor, a 
significant difference in signature between healthy 
and infected trees may not occur. This detectable 
reddish-brown stage may also only have a short bio 
window of four to eight weeks depending on the sever 
ity of weather conditions. For example, heavy rain 
or winds, may knock the needles off the trees. Past 
infestations in Saskatchewan have been of limited 
extent in isolated areas further increasing the dif 
ficulty of detection. Locally, these small areas, 
however, can have an important economic impact on 
stud mills or plywood mills. 
High resolution multispectral data from an electro- 
optical pushbroom scanner have been successfully used 
by Ahern et al. (1986) to map current year defolia 
tion in New Brunswick, but only at one level - 
presence or absence of defoliation. 
STUDY AREA 
The study site is located approximately 70 km south 
of the town of Hudson Bay in eastern Saskatchewan, 
Canada, covering an area of approximately 25 km 2 
along the Etomami River (NTS map sheet 63D/7, 63D/8) 
(Figure 1). The area is generally of low relief with 
numerous small lakes and wetland areas. The forest 
Figure 1. Location of study area - scale 1:250,000. 
cover is mixed hardwood-softwood with aspen (Populus 
tremuloides, Midix), white spruce, balsam (Abies 
balsamea, Mill.), black spruce (Picea mariana, 
Mill.), and jack pine (Pinus banksiana Lamb.) domi 
nating. White spruce, which is the main species 
affected by the budworm, occurs in mixed stands asso 
ciated with trembling aspen. Pure stands of white 
spruce rarely occurred in the study area. 
DATA ACQUISITION 
Three transects of MEIS-II data were obtained at the 
beginning of July 1985 at 5.5 m resolution (Table 2). 
Colour infrared aerial photography was acquired in 
the latter half of July and Thematic Mapper data at 
the end of August at which time the red-brown stage 
of the needles was still evident although some 
needles had fallen off the trees. Ground data were 
collected at the end of July. Airborne, oblique 
colour slides were taken during the ground data 
gathering period by helicopter. A number of stops 
were also made to check individual trees for levels 
of infestation. 
DATA ANALYSIS 
MEIS-II data 
The MEIS-II data were received in the form of com 
puter compatible tapes and were transferred from tape 
to disc on a DIPIX ARIES-II* image analysis system. 
Visual inspection of channel one of a total of eight 
channels showed a low signal-to-noise ratio and so 
was eliminated from subsequent analysis. The 
remaining seven channels were contrast stretched by 
using a linear or log transform and displayed on the 
colour video monitor. A colour image formed using 
channel 7 (red), channel 5 (green) and channel 4 
(blue) showed a shift in hue towards the edges of the 
swaths. Subsequently the edges were ignored and only 
the central portions of each swath analyzed. The 
natural colour image with channel 2 (red), channel 4, 
(green), and channel 5 (blue) showed an area of bud 
worm infestation which corresponded to the areas of 
infestation on the colour infrared aerial 
photographs. 
A number of biomass index enhancements using the 
formula: 
BI = SQRT ((F(1) - F(2)/(F(1) + F(2)) + 1.0 
where F(l) and F(2) represent the various channels, 
were also produced. The biomass index produced off 
set and gain values which were used to ensure that 
the output feature values lay within the intensity 
range of 0 to 255. Various biomass indices, using 
different channels, were combined through the red, 
green, and blue guns of the video display monitor 
(Table 3). Principal component and Martin Taylor 
enhancements were also produced (Taylor, 1973). 
Supervised maximum likelihood signature generation, 
unsupervised maximum likelihood signature generation 
and a real-time parallelipiped classification were 
performed. 
Thematic Mapper data 
Data from quadrant two, path-row 35-24 taken on 
August 26, 1985 on a computer compatible tape was 
transferred to disc on the ARIES-II image analysis 
system. The data were rotated 13 degrees and 
resampled from 30 m to 10 m to compare them to the 
* Mention of or failure to mention commercial trade 
names does not imply endorsement or criticism by 
the Government of Canada or the Government of 
Saskatchewan.