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BY 
ANNEXURE J 
THE USE OF AERIAL PHOTOS IN RECONNAISSANCE RESOURCES SURVEYS IN 
AUSTRALIA AND NEW GUINEA 
by 
G. A. STEWART 
Division of Land ‘Research and Regional Survey -  Common- 
wealth Scientific and Industrial Research Organisation, 
Land resources surveys made by the Division of Land Research and Regiondl Survey, 
C,8.1,R,0, are reconnaissance surveys (scale of mapping 1:250,000 to 1:1,000,000) to iden- 
tify, map and describe the country and to assess how it might be used, At this scale of 
mapping it is not possible to map each different type of soil or vegetation and the com- 
plex used in mapping and deseription is the "land system", defined as "an area or group of 
areas throughout which there is a recurring pattern of topography, soils and vegetation", 
The three essential features of a segment of landscape (known as a land unit) 
are the land form, ineluding steepness, length and shape of slopes and surface drainage 
characteristics, the nature of the soil or surface rock, and the vegetative cover, All 
of these are interdependent as well as being conditioned by the three major causal factors 
of landscape — climate, surface geology and geomorphic processes and history - which tend 
to be uniform over appreciable areas or vary in a reasonably regular pattern, Thus re- 
curring patterns of land units that are observed can be explained by the genesis of the 
landscapes. 
Land forms can be identified by stereoscopic study of aerial Photographs except 
where masked by tall dense vegetation, Also the height, density and cover of tree and 
shrub vegetation can be identified although modification by man poses problems in many 
areas, Soils cannot be observed directly except that, where vegetative cover is sparse, 
changes in colour and stoniness of the surface soll may result in different tones on the 
air photos, However, in general, soils can only be inferred by correlation with land 
form and vegetation, 
In the interpretation of aerial photographs we look not only for the particular 
combination of land form and vegetation corresponding to land units but the way in which 
they relate to other particular combinations to form complex "air-photo patterns" that 
correspond to land systems, Quantitative measurements of land slope or height, or tree 
height, size and density are standard measurement in various forms of detailed air-photo 
interpretation but cannot be used in this work because of îts rapid reconnaissance nature. 
Thus the air-photo interpretation is primarily a qualitative one of complex air-photo 
patterns, 
The surveys are made by teams of scientists including specialists in each of the 
elds dealing with inherent land characteristis, i.e, geomorphology, soils and vegetation, 
ris 
fielc 
Aerial photographs are used in all phases of the work, 
In pre-field planning work the aerial photographs are laid out in rough mosaics, 
communication are plotted, air-photo patterns are identified and, so far as is 
     
  
   
  
related to known causal factors and land characteristics, Field traverses are 
long convenient communications where possible, to sample the various identified 
air-photo patterns, 
During field work air-photos are used continuously in plotting movements in the 
field in locating the ehosen sampling sites, where the land characteristics are described 
in detail. Also, while travelling between sampling sites, correlations build up between 
d'A 
observable land characteristics on the ground and air-photo patterns are continuously 
checked, 
In the post-field laboratory work the air-photos are used to completely map the 
area concerned by interpolating from boundaries of air-photo patterns checked on the ground, 
aerial photographs to base maps 
boundaries are then transferred a 
of National Development giving a 
the Division of National Mapping, 
publication map of relatively high accuracy. 
    
In general, survey projects are planned on the basis of 3-1 months intensive 
nd.entails a total of from 312 to 418 months of laboratory work before and after 
o eomplete the project. The area covered in individual projects varies con- 
lg from 2,000 to 5,000 sq, miles in the Territory of Papua and New Guinea 
= Australian depending on the complexity of the 
and ‘the amount of information required, The gross 
the mainland is over 600,000 sq miles, while 20,000 sg, 
   
  
      
  
  
H E | 
o 70,000 sq miles on 
  
e Au mainland 
     
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