26 
3.1.5 Australia 
Ref. Urban, 7th United Nations Regional Conference, Tokyo, October 
1973. “With the introduction of the first orthophoto mapping instrument in 
the State of New South Wales in 1971, it became apparent that large scale 
mapping of urban areas could be undertaken effectively and efficiently as 
series of orthophoto mapping within a reasonable time scale”. Since 1971 
much orthophoto mapping at scales of 1:2,000, 1:4,000 and 1:10,000 has 
been carried out. Contours, produced by conventional stereo plotting, have 
been overprinted onto the maps. 
The Greater Metropolitan Area of Sydney was orthophoto mapped at 
1:4,000 scale. “The production of orthophoto maps is not possible in high- 
rise areas due to the lean-over of buildings. It is suggested that 4 storeys is a 
practical limit for 1:4,000 orthophoto maps using a wide angle camera 
(c = 6”). The centre area of Sydney has therefore been designated a 1:2,000 
line mapping area". 
32 A New Orthophoto Producing System 
As is noticeable from the above examples, any multi-purpose photo 
mapping requires height information in the form of contours and spot heights, 
as overprints or on overlays. In all the examples, the height information has 
been produced by conventional stereo plotting, often from a separate set-up 
of the stereo-model on another machine from the one used for the profiling, 
which in all cases was done manually. Going thus twice through the complete 
stereo model, first for profiling and then for contouring, is uneconomical. To 
obtain the highest possible height accuracy, conventional stereo-plotting of 
contour and/or spot heights is a must. Based on this necessity, a new ortho- 
photo producing system has been developed whereby the production of the 
orthophotos is fully automated. This off-line system which, in my opinion, 
is highly to be recommended, includes the following phases. 
a) Set-up of the stereo model in a conventional stereo plotter, provided with 
proper means of fast automatic registration of model co-ordinates, so that, 
when following the contours in the stereo model to produce the contour 
plot, contour points are automatically digitised, at short intervals. Also 
characteristic height points are digitised; 
e