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whereby a plantation inventory is carried out using aerial photos for stratification pur- 
poses, together with angle eount sampling (a fast modern sampling procedure) within the 
various strata (in this case site index as indicated by top height of the stand). The 
necessity for large scale photography is basic to the method, and proves to be rather ex- 
pensive, 
A number of attempts have been made to devise photomensurational techniques suita- 
ble for use in Australia: that is, endeavouring to find some fixed relationship between 
certain measurable and unmeasurable variables in the forest stand, 
Apart from isolated instances, these attempts have not been successful, especially 
those applied to the natural Eucalypt forest, In the past the selective logging of the 
forest has altered the physical nature of the stand to such an extent that no suitable 
relationships ean be recognised, Of course, this is not the fault of the photos, but 
more an inherent characteristic of the forest. 
During the aerial inventory of Norfolk Island, an external territory of the 
Commonwealth, a satisfactory crown diameter/stem diameter relationship was established 
for open grown Norfolk Island Pine (Araucaria excelsa) and used in volume determinat ions. 
Naturally, there are a number of factors that can affect the quality of an 
interpretation job, Firstly, consider the interpreter himself, Experience has shown 
that a certain type of person is more adapted to this work, Sims and Hall (1955 and 1956) 
outlined the desirable characteristics in persons suitable to be trained as interpreters; 
they included keen observation, logical deduction, patience and a controlled imagination 
as well as the more obvious need for high optical acuity and an extensive general knowledge 
especially in the particular field likely to be encountered. Any lack of these basic 
characteristics means less chance of an accurate and reliable interpretation, Of course, 
the temperament and general health of the person is rather critical, 
The scale of the photo is perhaps the most important single factor concerned. 
If a mission is specially flown for the particular project, then scale can be ordered to 
suit the work invoived, but in most cases the forester finds himself using photos origi- 
nally flown with some other purpose in mind, Occasionally, a group of different interests 
are combined into the one mission, but this approach usually results in unsitable photo- 
graphy for everyone. 
The following scales have found use in forestry work : 
1:31,680 suits the determination of location of broad forest type boundaries, 
e.g. , between Eucalypt forest and rain forest, 
1:15,840 suits tree height measurements. and detailed forest interpretation, ete., 
e.g. , between ridge type and gully type within a Eucalypt forest type. 
1:7,920 is excellent for very detailed interpretation especially in coniferous 
plantations, 
The optimum scale from a forester's point of view is at 1:15,840, or thereabouts, 
as it is relatively economical to fly, and yet useful tree height determinations can be 
made, 
The age of the photography can be of the utmost importance in certain circum- 
stances, The interpreter needs to be constantly aware of changes that could have taken 
place in the forest after the photographs were flown, 
There are many other factors involved, for example, type of print, season of 
photography, etc,, but these will not be dealt with in detail, 
The advantages to be gained by the use of air photographs in forestry are 
extensive, The speed and relatively low cost of the job are perhaps its main virtues, 
but the ability to obtain more accurate overall information than previously is very 
important also. The variety of uses to which the one set of photos can generally be 
put, very quickly recoups the initial outlay, 
Finally, it is desired to re-emphasise the point that the photo as such does 
not completely eliminate the field work associated with Forestry problems, In many 
cases, the photo can do away with quite a high percentage of it, but generally speaking 
as far as forestry and forests are concerned, field work is the key to complete and 
economic use of aerial photographs. Air photos are now a most important aid to the 
forester, and I am sure that the extent of this aid will grow in the future,