OPTIMUM RATIO OF PHOTO-FIELD PLOTS 
FOR AERIAL VOLUME AND AERIAL VOLUME 
GROWTH REGRESSION CONSTRUCTION 
D.A. Stellingwerf* 
ABSTRACT 
The calculation of the optimum proportion of field/photo plots for a fixed 
cost ratio of field and photo plots is done for spruce in a 3000 ha forest 
covered region in Austria 3 considering two cases: 
1) the optimum proportion for the construction of a volume table and 
2) the optimum proportion for the construction of a gross mean volume growth 
table. 
Linear regression equations are taken both for the volume table and the 
volume growth table. 
In addition to standard error and cost calculation for the two cases 3 
standard error and cost figures are also given for pure field plot enume 
rations not using aerial photographs. 
In the given examples the combination of photo and field plots is always 
cheaper than the field plots alone. However 3 additional expenses for photog 
raphy and. other applications of photography for management purposes should 
be considered in order to have a proper judgment for the use of aerial photo 
graphs for such management purposes. 
When 3 however 3 the construction of the tables for volume and growth is com 
plete j the application of these tables is always much cheaper than pure 
field enumeration. 
RÉSUMÉ 
Cet article donne les résultats d'un calcul qui concerne le rapport optimal 
qui existe entre le nombre des unités de sondage sur le terrain et sur les 
* 
Head of Forestry Dept. , Chairman of Natural Resources Dept.