I 
| 136 ANNOUNCEMENT OF PRESENTED PAPERS 
| cases the forest may not truly reflect growing happy to be able to join this working group, 
| conditions and there can be confusion about which gives us the opportunity to contact dif- Ein 
| actual site conditions, unless one has a good ferent specialists, both in the field of photo- for: 
understanding of the position. grammetry and of photo-interpretation. 
| 
| Prof RUELLAN: I do not quite understand Mr A delegate, probably from India, comments (So 
| Miller’s remarks, and would like to make the that it seems of importance to create a team of aeri 
| following statement. I quite agree that there are specialists in the field of photo-interpretation to 
| relations between photo-interpretation and the study these problems in cooperation. 
| different fields of science. But particularly in : 
| tropical countries, I have the impression that we CHAIRMAN: Agrees with this suggestion and pap 
| are still in the beginning. We have to improve proposes to start with the announcement of the Rum 
| the techniques to get better knowledge. I am presented papers. ) 
| SCO] 
| that 
Presented Papers 
Pieter Steiner's Paper 
W. von Lahr (Forsteinrichtungsamt Koblenz) 
Vorlüufiger Bericht über die Entwicklung eines 
Verfahrens zur Aerophotogrammetrischen 
Hóhenwachsmessung von Waldbestünden. 
(Provisional report on a method of measurement 
the height increment of a forest stand by aerial 
photographs) 
As only a limited number of reprints of this 
paper was distributed by the author during the 
congress, a short summary will be given here. 
The height of a forest stand was measured on 
two different sets of aerial photographs, photo 
scale approx 1 : 15.000. Exposures were made 
with a time interval of 8 years. Measurements 
were made by the stereotope. An accurate 
determination of the height increment was ob- 
tained. This project will be continued. 
G. Wolff (Forsteinrichtung Eberswalde. G DR) 
Zur Verbesserung der Methodik von Holzvor- 
ratsinventuren mit Hilfe des Luftbildes. 
(An improved method of forest inventory by 
aerial photographs) 
As only a limited number of copies was 
distributed during the congress the paper will 
be given by summary. 
Based upon current research studies of 
forest inventory methods applied by the Forest 
Service of the GDR, the author put forward the 
following results. Stratification in evenaged 
forest stands, based on the interpretation of 
aerial photographs in combination with an 
additional ground check, resulted in higher 
efficiency in forest inventory by sampling 
methods. With a stratification system based 
upon height and density classes, a system of 
systematic sampling by different sampling per- 
centages within the various strata could be ap- 
plied. The percentage of sampling within each 
stratum was based upon the amount of variation 
within the stratum and the costs of making these 
measurements. 
Compared to former sampling methods with- 
out aerial photographs this new technique 
resulted in a higher accuracy in timber volume, 
while the cost remained the same. Remarkable 
results were already obtained with a relatively 
less detailed stratification system. The applica- 
tion of a mechanical computing system by 
punch cards effected great economy in the 
calculation procedure. 
H. Ericsson (Forestry Commission Sweden) 
Concerning Accuracy in Measuring Tree and 
Stand Heights on Aerial Photographs. 
Measurements of tree and stand heights were 
executed on different kinds of photographs, 
different photo scales, different flying heights 
and for different illumination conditions (sunny 
weather with a clear sky or with a slight over- 
cast by clouds). 
For the measurements also different kinds 
of instruments were applied as the common 
mirror stereoscope in combination with the 
parallax bar, the Wild A7 and the Balplex. 
Results obtained were showing that there was 
a slight difference in the rate of accuracy as a 
result of the photographic material used and the 
measurement instrument applied for this pur- 
pose. In most cases it was apparent that there 
was not much variation in the systematic as well 
in the accidental errors. Systematic errors vary 
mainly between 0 and —5 m, whereas the varia- 
tion of the accidental errors was between 1 and 
2 m. 
R. Totel (Forstinstitut Eberswalde GDR) 
  
  
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