experienced observer was around 3m and that by a beginner was
around 5m.
The average measurement error by the experienced and the
beginner was 1.3m and 3.4m respectively. Considering the
analogue photography, accuracy achieved by using stereoscopic
is with in the range of about 2m. Hence, in our case, even for
the beginner if we skip the mistake in measurement due to
carelessness accuracy close to 2m was possible. The beginner
was able to get the result with in the half day of starting to use
the Morittai for the first time. The training was provided for half
day and the person was able to do the measurement of 40 points
within two hours.
4. CONCLUSION
In this study, we implemented and reviewed the functionality
needed to grasp the information of forest resources by making
use of digital aerial photography. The major advantage of
Morittai, our system, is stated below.
(1) The results showed that it was possible to get good data
from aerial photography even for beginners with no
experience of photo interpretation using our system.
(2) Since the stereoscopic view of the forest can be displayed in
the PC monitor or projector, the system can be used for
technical guidance to the beginner or can be used for expert
consultation to multiple person at a same time.
(3) Compared to digital orthoimage, the system can be used to
visualize the tree trunk in a high definition. Moreover, the
decay situation of trees can also be visualized more easily
with a high resolution compared to the digital orthoimage.
(4) Since timber volume can be calculated from the aerial
photos, this system reduces the cost of field survey.
However, in the cases where the ground surface is not
visible due to high vegetation density, the evaluation of
ground height from the DTM constructed from LiDAR data
will improve the accuracy of timber volume measurement.
This system is being utilized in companies and research
institutions that deal with forest resources and management.
Furthermore, this system is also adopted in the training
curriculum for the forest information technologist.
5. REFERENCE
Gagnon, P.A., Agnard, J.P., Nolette, C., 1993. Evaluation of a
softcopy photogrammetry system for tree-plot measurements,
Can. J. For. Res. 23, pp. 1781-1785.
Millera D. R., Quineb C. P., Hadley. W., 2000. An investigation
of the potential of digital photogrammetry to provide
measurements of forest characteristics and abiotic damage,
Forest Ecology and Management, Vol. 135, pp. 279-288.
Acknowledgements
The authors would like to thank Japan forestry agency's digital
forest information development project for supporting this
research.
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B8, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
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