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miles in New Guinea have been surveyed, 
: The scale of the aerial photographs used are mainly 1:50,000 and these have been 
found to be suitable for our needs, In some places the only coverage available was 
1:15,000 and 1: 25,000, Because of the small areas covered on each air-photo the air-photo 
patterns were more difficult to recognise and map and many more air-photos had to be 
handled, Numbers of air-photos is not a great problem for New Guinea surveys, where only 
200 to 500 photos need to be studied, but some larger mainland surveys require the handling 
of up to 12,000 aerial photos for a two-year project, 
This broad scale qualitative photo interpretation for the definition and des- 
eription of complex types of country is a different level of interpretation to detailed, 
more quantitative, photo-geology, photo-forestry or photo-soils mapping but the contri- 
bution of aerial photos to labour saving is equally great, If these surveys were done 
without aerial photos five times the amount of field work would still not yield an equal 
degree of detail and accuracy, In faet, aerial photos are so essential to the method of 
broad scale survey that surveys will not be undertaken unless air-photo coverage is 
available, 
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