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account is given of the methods and results of the examination. In addition
to this work, some investigations concerning volume measurements of
forests on aerial photographs were executed as exercises at the university.
It can be concluded from the existing material, that volume measurement
on aerial photographs is possible in Finnish conditions, and that the me-
thods can be put into practice, specially in northern Finland.
For the present, estimation of the state forests, and estimation of the
stand in the archipelago will be made on the base of aerial photographs.
The methods are not yet worked out.
Germany:
Estimation of cubic volume by using empirical volume tables or sample
plotting.
Concerning the estimation of timber-stock, which could not be continued,
we refer to the work of Professor Hugershoff and his pupils.
Sweden:
The crown diameter has proved to be a useful ancillary factor when
estimating the breast-height diameter of a tree. It is, however, often hard
to see and measure the crowns, particularly when they are small, densely
packed, or in shadow. The quality of the photographs, as well as the scale,
are of great importance.
Stand density appears clearly in the picture and can be used for many
purposes.
The volume of large isolated trees is approximately estimated from preli-
minary studies of crown diameter, tree-height, and sometimes density.
Sample plot volumes have been estimated by comparing them with photo-
graphs of similar experimental areas, where estimates have previously
been made on the ground (cf.site quality). This method has yielded rather
uncertain results for isolated trees and stands, but for large forest areas
it appears to be practical and useful in cases, where there is relatively little
need for accurate results. It should be possible to develop these methods
and they may have great importance in the future.
U. S. A.:
Of those who are using aerial photos for timber estimation, about half
use photo height measurements and about half use crown diameter measure-
ments of the trees.
The purposes of using the cruise are varied and include cruises for manage-
ment plans, purchase or sale, policy statements, logging plans, national
inventory, etc. Many of these require different degrees of accuracy. The
lowest degree of accuracy being for national inventory and the highest
for purchase or sale. All methods used are supplemented by ground cruises.
In practically all cases the merchantable portion of the stem of the tree
is used. Merchantable in pulp wood would mean a 2" to 3" top, while
merchantable in saw timber would be to a top diameter limit of about
50 °/o of the DBH.
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