channel to create a bitmap for "Class A" given a minimum grey level of 250 and a maximum of 255 and 
another bitmap for "Class B" given a minimum grey level of 200 and a maximum of 249. "Class A" represents 
"deeply gouged or exposed compacted mineral soil"; "Class B" represents "exposed mineral soil or possibly 
woody debris". 
3.0 RESULTS AND DISCUSSIONS 
3.1 Digitized Color Image 
The contrast-stretched color images produced from the computer digitized data sets and displayed on the color 
monitor were superior in comparison with the original aerial photograph. Color and brightness differences 
between landings, roads and skidroads were quite distinct. Part of the landing area at the edge of the forest 
was obscured by the shadows of tall trees. "Class B" - "exposed mineral soil or possibly woody debris" on the 
landings, roads and part of the skidroads showed up as a bright white color. The color of the landings, roads 
and some skidroads partly reflects the depth of cut as the ones with deeper cuts or greater usage were usually 
more distinct. Digitization of the original aerial photographic print permitted display of CP #140 Units #29 
and #32 on the color monitor and the assignment of any color or light intensity to each of the three channels 
of the enhanced data sets to obtain the most desirable combination of colors and brightness. The combination 
of the contrast-stretched enhanced red, green and blue digitized color image channels produced from the 
computer digitized image data sets and displayed on the color monitor with red, green and blue filters, 
produced a superior image when compared with the original aerial photograph. 
3.2 Estimates of the Landings, Roads and Skidroads 
Landings, roads and skidroads were sketched manually using a "cursor" to trace their outlines on the color 
monitor. Pixel counts were made within each of the three outlines of landings, roads and skidroads. Table 
1 shows a comparison of the results of operator-assisted estimates of the extent of soil disturbance with a 
ground survey for CP #140 Units #29 and #32. 
With the ground survey sketch map (Unit #29) showing the locations of the landings, roads and skidroads as 
a guide, the difference between the tracings of the landings, roads and skidroads on the color monitor and the 
ground survey was very small, 0.003 ha or 0.03%. However, without the aid of a sketch map (Unit #32) the 
differences were greater, 0.085 ha or 1.68%, because some of the skidroads were covered by woody debris and 
were not very distinct on the digitized image. Table 1 shows that the computer operator-assisted estimate for 
skidroads was 5.02%, whereas the ground survey estimate was 1.54%. This difference of 3.48% was due to the 
fact that the computer operator manually traced the skidroad network using the color monitor image as guide 
but part of the skidroad network was not considered by the ground surveyors as skidroads at all, and vice versa 
for landings and roads. Therefore, an operator who is familiar with the clearcut site could probably be able 
to sketch the locations of landings, roads and skidroads more accurately. 
3.3 Threshold Estimates of Exposed Mineral Soil 
Differences in color and degree of brightness, corresponding to "Class A" - "deeply gouged or exposed 
compacted mineral soil" and "Class B" - "exposed mineral soil or possibly woody debris", were detected as grey 
level "250 to 255" and "200 to 249", respectively. Pixel counts of "Class A" and "Class B" for Units #29 and 
#32 were obtained from the results by thresholding the bulk radiometric enhanced blue filtered channel. Table 
2 shows the results of threshold classification for CP #140, Units #29 and #32. For Unit #29, only 1380, 3331 
and 3822 pixels within areas for landings, roads and skidroads, respectively, were classified as the total number 
of pixels for both "Class A" and "Class B", whereas the manually traced areas within the landings, roads and 
skidroads were 2136, 3537 and 7743 pixels, respectively. The differences between the number of threshold 
125