——?iÀ
Table 1. Data of the Aerial Photographs Used for the Investigation.
| | Eu de =
| |
Flying | : Wind Relative
Track | altitude | p Time ef Cloud | velocity |length of | Base
lm | pnotogranay | | m/sec. | shadows | Fano |
| | i
21a | 1280 | 18/7—57 10.35 | Overcast | 2 = / 05 |
31 1580 | 18/7—57 09.50 | Overcast 2 = / 0.34 |
41 | 1880 | 18/7—57 10.10 | Overcast 2 e 0.59 |
4l o 1890 | 22/7—57 08.30 | Clear | 1 14 1 057 |
15a | 3190 25/5—56 10.40 |Clear | 38 09 | 049 |
Research Area
For measuring the tree height a felling area of about 7 hectares was
used. The difference of level between the lowest and the highest point
amounted to about 6 metres. The ground cover consisted of grass of
varying density and height (1—4 dm). But a few shrubs and stones
were found. In the felling area 42 single trees (Scots pine) were mea-
sured and described, and identified and marked on the photographs.
For the measurements a Blume-Leiss tree-height measurer was used.
In the area a number of sample plots were laid out in various types
of stands.
For determining the scale of the prints two stretches were measured
on the ground,
Measurement and Treatment of the Material
Tree Height
The measurements have been grouped in the following way:
l. Measurement on paper prints in mirror stereoscope (ocular magni-
fication 8x and 3x) and micrometer. The prints were enlarged or
reduced to the scale 1:10 000 and high-glossed.
2. Comparative measurements on the scale of the contact Copy.
3. Measurements on negatives (mirror stereoscope and A 7, diaposi-
tives for Balplex).
For all measurements in mirror stereoscope a Wild mirror stereo-
scope was used. The measurements were made by operators with a long
experience of this instrument. The measurements in A 7 and Balplex
were performed by the ordinary operators of these instruments.
Stand Height
For measuring the stand heights the prints which gave the highest
accuracy in measuring the tree heights were used. The measurements
were made in mirror stereoscope (ocular magnification 3x) by persons
educated in forestry and trained in making such measurements and
estimations.
