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PHOTOGRAM METRIC ENGINEERING 
has found it appropriate to plan loggings by studying aerial photographs. The 
logging areas are marked and described by using Old Delft scanning stereo 
scopes. This chart-room work is checked in the field. Korsnas AB is another big 
forest company, that has resolved to use photographs instead of drawn forest 
maps. Much attention is paid to the quality of the photographs as well as to ar 
ranging the photographs for comfortable use in the field. In connection with ex 
pensive uprooting of timber by unusually severe storms, aerial photographs have 
been taken of the areas in question and their limits determined by means of inter 
pretation. It has also been possible by these means to decide by which routes the 
felled lumber should be transported. In this way great profit has been derived 
from what otherwise would have been a more or less total loss. 
In the United States, access and spur road locations are first determined 
under the stereoscope or on topographic maps made by photogrammetric meth 
ods. Photos are used by foresters as a guide in locating rock or gravel for road 
construction. Photo interpretation is being relied upon to provide information 
on stream conditions when water transport of logs is contemplated. 
Aerial photos are commonly used to search out scattered patches of mer 
chantable timber, or to determine the boundaries of an area needed in scattered 
timber to include the desired sale volume. Residual stands are carefully studied 
on aerial photos to establish the feasibility of a salvage or relogging chance. 
Snag sales are sometimes based on photo counts. Numerous operators have their 
newly logged areas photographed at the end of each logging season to provide 
(1) a cutting record for inventory, (2) location of new roads, (3) condition of the 
residual stand, and (4) extent of slash problem, and other pertinent informa 
tion. Timber sale officers often use photos to make quick checks on the feasi 
bility of volume estimates submitted by cruisers. 
AERIAL PHOTOS LOCATE FOREST INSECT DAMAGE 
In the United States two forest insect laboratories—one at Beltsville, Mary 
land, and the other at Portland, Oregon-—have made extensive aerial photo 
graphic and interpretation tests for the detection and appraisal of insect dam 
aged timber. Because of the dynamic nature of insect populations, photography 
must be restricted to sampling methods due to cost, and to films and filters 
which record a discoloration of the normally green forests. Preliminary tests 
were aimed at determining whether certain types of insect damage could be 
detected on film; these tests indicate that infrared film is of no value, panchro 
matic film with an A-25 filter can be used for certain kinds of damage, but that 
color film produces the most accurate results when the interpretation is com 
pared with ground study plots. Scales of the color photography varied from 
1:1,200 for detecting weevilled white pine leaders, to 1:5,000 and 1:7,920 for 
identifying insect killed pine and fir trees. If a reasonable degree of interpreta 
tion accuracy can be determined for each type of insect damage, sampling 
surveys will be designed so that appraisals of timber damage can be mide from 
the color pictures. Any aerial method has the limitation of being able to detect 
only faded trees; it does not account for surrounding infested trees which are 
still green but dead. Only ground inspection will reveal this ratio. 
PHOTO TECHNIQUES ARE VITAL TO FOREST FIRE CONTROL 
Forest fire protection is an activity in which aerial photo interpretation is 
playing a vital part. This is particularly true in the U. S. where there are vast