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cases where, because the stands are too dense, the ground cannot be seen and
therefore no measurement of tree height can be made?”
Answer by Mr. Moessner: *Based upon thousands of routine heihgt meas-
urements which we have made in the Central States and the experimental meas-
urements I have made on photos of Japan, Ryukyus Islands, East Pakistan,
Norway, Alaska, and many parts of the United States, I believe the difficulties
of parallax measurements in dense stands appear greater than they actually are.
On almost any set of photos we can select an area where it is impossible to see
the ground and hence to make a height measurement. At the same time, in al-
most any stand openings can be found. The forester merely needs to select open-
ings at the same relative topographic positions and to measure trees having the
same appearance as those on his plot, to be within the required accuracy. If the
stand is even-aged on flat terrain, such as swamp or jungle, probably one or two
accurate height measurements along a river will suffice for the stand. If the ter-
rain Is mountainous or if the stand is all aged, sufficient openings for height
measurements will almost surely exist. To date I have never found the aerial
estimating of a stand impossible because I could not make height measurements."
Following Mr. Moessner's presentation, papers also were given by W. Hall;
T. Lomasson and C. E. Waldo; D. J. Belcher; and D. L. Leedy.
The full text of each of the above papers, in English, and an abstract in
French appear elsewhere in these Archives.
INTRODUCTION OF CAPTAIN THOREN BY LCDR COLWELL.
The third series of Commission VII papers pertains to *Photographic In-
terpretation in Military Intelligence."
The chairman for this phase of Commission VII is Captain Ragnar Thorén
of the Royal Swedish Navy who has specialized in military photo reconnais-
sance and photo interpretation for nearly 20 years. It was as an expert in these
two important branches of military intelligence that Captain Thorén joined the
Finnish armed forces as a volunteer under Marshal Mannerheim, in their heroic
fight against the Russian communists in World War II. Captain Thorén's ex-
tensive experience as a combatant officer has given him the sound approach to
photographic intelligence which can come only from such experience. He 1s
already known to many of us as an unusually capable and friendly person, as a
result of his visit to the United States in 1947. During our 1948 World Con-
gress in the Netherlands Captain Thorén presented an excellent paper entitled
“Photographic Intelligence and Photo Interpretation,” which was very favor-
ably received. It clearly established him as one well qualified to organize and
preside over the panel of papers which we are about to hear.
It is both an honor and a pleasure to introduce your chairman for today's
meeting, Captain Ragnar Thorén.
Acknowledgment by Captain Thorén:
Thank you for your very kind introduction, Commander Colwell. It is
indeed a pleasure to visit the United States again, to meet many old friends, and
to make many new ones.
