ication of his photo- 
me of exposure with- 
camera did not have 
was determined ana- 
from a non-metrical 
racy requirements of 
1 Ektar lens. It was 
etrical purposes be- 
ame setting as those 
o with the top of the 
) with the lens in its 
ard the image plane. 
lens positions were 
obable error of only 
that the film was not 
able metrical proper- 
of the same type of 
tortion in the corners 
ow order of accuracy 
ossible errors. He 
looked like popcorn. 
object space. The 
were computed and 
nch for the far end of 
ase. It was pointed 
lately in front of the 
irrelevant since the 
length. An arbitrary 
he control data con- 
listances to the tail 
ieasured on identical 
ghts from the camera 
ions the angles sub- 
ween the lights were 
which were measured 
d. These data were 
a with respect to the 
n the horizon (which 
were determined with 
spect to the arbitrary 
the functions of tilt 
e ground coordinates 
ed value of the skid 
iphic evidence would 
e error was less than 
' was burdened first 
trical science, then 
ing its accuracy in a 
of the photographic 
operties following 
as those of lens and 
of orientation could 
| errors could be de- 
n this case accuracy 
it would have cost if: 
hotographic coverage 
(529) 
SOME UNSOLVED PROBLEMS IN FORESTRY AND SUGGESTED 
SOLUTIONS 
by 
John C. Sammi. 
Aerial photographs can and are being used to aid the forester in his work. 
They are helpful in such diverse problems as the preliminary location of roads 
and trails, areas to be set aside for fishing preserves, game reserves, administra- 
tive sites, the relocation of property lines, estimating the volume of timber on 
given areas and for many other purposes. The most intensive use of aerial pho- 
tos has been in the field of timber estimating. 
Timber estimating in the United States is a somewhat involved problem 
because of these factors: 
The character of the forest differs from one forest region to another as the 
mixed stands including many hardwood species in the hilly country of the 
northeast to the relatively open pine stands in the level country of the south- 
east. 
The size of the area to be cruised which may vary from about 40 acres to 
2 million acres. 
The purpose of the cruise which may be for purchase or sale of the tract, 
for a logging plan, for management plan or for a general reconnaissance or for 
some particular species such as peeler logs, cherry for furniture, walnut for gun 
stocks. 
The problems that arise, and most of them have not been solved to our 
complete satisfaction, are all of the problems that pertain to obtaining better 
photographs. The factors involved have been very ably pointed out by Doctor 
MacDonald as starting with the photographic plane and continuing through 
the camera mount to finally, the processing of the photograph and to the 
interpreter. 
What Has Been Done In The Past. 
Many of these problems have had to be recognized and some immediate 
decision made on how to carry forward a particular project. In some cases the 
decision was based on ocular observation. In comparing two photographs by 
this method reasonable results were obtained as long as the differences between 
the two photographs was readily capable of being detected. The decision was 
then made to make use of the factors governing the better photograph. In 
some cases decisions were made that resulted in a compromise. For instance, as 
Dr. Spurr has so well pointed out, infra-red photography makes it possible to 
readily differentiate between hardwoods and softwoods, while panchromatic 
photography presents much more detail. The compromise he suggested is the 
use of the infra-red film with a yellow filter which has some of the advantages 
and some of the disadvantages of both of the extremes. Incidentally, another 
solution to this problem has been developed by a contractor in the State of 
Washington. He has flown the area with two cameras taking pictures simul- 
taneously, one loaded with infra-red and the other with panchromatic film. 
41