310 
SYMPOSIUM PHOTO INTERPRETATION, DELFT 1962 
case when the size of the single parcels becomes 1 mm 2 or smaller on the map. 
We are obliged to simplify the land use patterns to represent them on the map. 
To be free of such a skill demanding mapping technique, photomaps of a 
suitable scale should be introduced as the base map. Unfortunately, however, 
seasonal changes of land use can not be traced on photomaps. Such informa 
tion should be indicated on overlays by using the data obtained in field in 
vestigation. 
Selection of the scale of the photomaps will depend on the scale of the aerial 
photographs which be used for the land use survey. Aerial photographs on 
the scale of about 1 :40,000 have been used for land use survey. However, 
aerial photographs on a scale of about 1 : 10,000 to 30,000 taken for mapping 
by modern cameras have gradually come into use. Considering such a scale of 
aerial photographs and the complicated land use pattern, we think that it 
will be better to compile photomaps on the scale of 1 : 25,000 and 1 : 50,000. 
Introducing photomaps with overlays, it will also be possible to show the 
data necessary for regional planning. 
In the near future, the problem of time economy should be solved by in 
troducing the technique of making photomaps. At the same time, we have to 
investigate the advantages and disadvantages of photomaps with overlays 
compared with the land use maps in existence. 
Discussion 
To a question by Dr. Steiner (Switzerland) how the execution of photo coverage is organized 
in Japan, the speaker answered that aerial photographs are taken by both governmental 
organizations and private companies. The Geographical Survey Institute (G.S.I.), however, 
keeps a central registration of all aerial photography in the country. 
Dr. Tremolieres (France) asked what scales were applied in the G.S.I. for different purposes. 
Dr. Nakano gave the following outline: 
map scale photo scale 
1. 
land use 
1 : 50,000 
1 : 40,000/25,000 
2. 
landform classification 
1 : 50,000 
1 : 40,000/25,000 
3. 
land use for land improvement survey 
1 : 20,000 
1 : 20,000/25,000 
4. 
landform classification for flood prevention 
1 : 25,000 
1 : 20,000 
5. 
photomap for regional planning overlay on: 
1 : 25,000 
1 : 25,000 
6. 
photogeological survey for highway construction 
1 : 25,000 
1 : 25,000 
Dr. Schmidt-Kraepelin (B.R.D.) inquired after the cooperation between organizations in 
different fields of science with regards to photo interpretation. The speaker mentioned that 
special committees have been set up by the Ministry of Agriculture and Forestry for land 
classification and land use mapping. He himself was a member of this latter committee, and 
suggested the use of aerial photographs. Asked about the experiences in Japan with infra-red 
and colour photography, Dr. Nakano said that a special study group had been established 
to study these kinds of photography. Colour photography is still in an experimental stage.