26 
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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