2.0 METHODS 
2.1 Test Site 
The study areas were located near Likely, in the Cariboo Forest Region of south-central British Columbia, 
Canada. The specific site which encompassed Units #29 and #32 of CP (Cutting Permit) #140 in the Cariboo 
Lake Logging Trial (Krag and Webb 1987) was clearcut in the winter of 1985 using small crawler tractors for 
yarding the logs. 
2.2 Ground Survey 
Units #29 and #32 of CP #140 were surveyed on the ground in January, 1986. The areas disturbed by 
landings, roads and skidroads were determined by measuring the widths at intervals and the lengths. The size 
of Units #29 and #32 were measured using boundary traverse survey data. A sketch map, showing the 
locations of landings, roads and skidroads was provided for Unit #29 but not for Unit #32. 
2.3 Aerial Photography 
Units #29 and #32 of CP #140 were photographed on July 20, 1985. A Wild RC 10 camera with a 304.03 
mm lens was mounted in a Piper Navajo-31 aircraft for the photographic mission. Kodak aerochrome 2445 
color negative film (229 mm X 229 mm) was used. The flying height was about 1525 m above ground level 
and the average scale was 1:5000. 
2.4 Computer Digitization 
The Infrascan Image Processing hardware and software consists of a PCvision Plus 512 frame grabber (1024 
X 512 X 8 bit), a solid-state CCD (Charge Coupled Device) monochrome camera 4800 series (high resolution- 
high sensitivity) by Cohu Inc., ITEX/PC Vision Plus software, an Electrohome black-and-white (B/W) monitor, 
a camera mount Nikon lens adapter with red, green and blue filters, and an interface for the Number Nine 
card. The Infrascan Image Processing System is capable of scanning both translucent and opaque materials. 
Thus, B/W or color transparencies or prints may be scanned. The image densities were based on a gray scale 
ranging from 0 to 255. The color aerial photographic prints of Units #29 and #32 were scanned using red, 
green and blue filters. The images were transferred directly from the PCvision frame grabber to a Number 
Nine card and a Mitsubishi color monitor. The three image data sets were then transferred from the Number 
Nine card to the image database using Perceptron (PCI) image analysis software for further digital image 
analysis. 
2.5 Digital Image Analysis 
Two digital image analysis techniques were used: (a) manual tracing with a "cursor" to sketch landings, roads 
and skidroads on the color monitor and (b) a procedure designed to provide consistent areal estimates of soil 
disturbance for clearcut units. 
The procedure in (b) involves: (1) isolation of the study area; (2) determination of the minimum and maximum 
grey level values for each of the three image channels; (3) contrast stretching the three image channel data sets 
using the minimum and maximum grey level values of the study area; (4) enhancement of the original image 
data sets to form a superior image using the contrast stretching data in (3); (5) generation of grey level print 
out for each of the three image channel data sets for inspection of color and brightness of image corresponding 
to grey level; and (6) application of the thresholding routine to the enhanced blue filtered database image 
124