matically controlled orthoprojectors, consider- 
ably improves the profitableness of the use of 
digital terrain models (D.T.M.). Although their use 
is limited to a few countries, the sub-products 
such as stereo-orthophotography introduce — at 
reduced cost — the third dimension, a fact that 
should facilitate the study of road construction 
projects. 
Mr. B. Cabrera (Mexico) reported that the Mexican 
Ministry of Public Works makes intensive use 
of photogrammetric techniques in carrying out 
autoroute projects (300 km per year, scales from 
1:20000 to 1:1000), but that the D.T.M. are not 
considered accurate enough. 
Mr. C. Slama (U.S.A.) told the audience that the 
U.S. Academy of Sciences — in cooperation 
with the American Society of Photogrammetry 
— has published a "Summary of the Use of Pho- 
togrammetry for Highways", giving a general view 
of the state of affairs. 
Presented Papers 
Author: Dr. H. Kasper (Switzerland) 
Title: Flugaufnahmen aus Helikoptern zur 
Feststellung von Strassenscháden 
PP 1V/25 
Dr. Kasper said that damage done to road sur- 
facings could be measured from photographs 
taken from a helicopter with an accuracy reaching 
1 cm. He mentioned the paper of Dr. K. Kôthe 
(F.R.G.) with similar accuracy for railway mea- 
surements. 
Author: 
Title: 
Mr. G. Hallert (Sweden) 
The Application of Aerial Photoin- 
terpretation to Road Design in Swe- 
den PP /V/21 
Mr. Hallert pointed out that road construction 
was considerably facilitated by the use of photo- 
interpretation. With the help of photointerpreta- 
tion the types of soil are inventoried so as to 
determine the alinement. The scales of photo- 
graphy (1:30000, 1:13000) enable mapping even 
at 1:2000. 
Panel Discussion 
Topic: Applications of Digital Terrain 
Models 
Moderator: Dr. C. Ternryd (Sweden) 
Panelists: — Dr. K. Kraus (Austria) 
Dr. R. Murai (Japan) 
Mr. M. MacLeod (Canada) 
Mr. R. Mahan (U.S.A.) 
Mr. B. Cabrera (Mexico) 
Mr. B. Adolfsson (Sweden) 
The question of the day was the future of Working 
Group IV/1: should it continue its work or should 
it be dissolved, and this after 16 years of exis- 
tence, in the course of which photogrammetry 
and digital terrain models have progressively 
become a classical procedure for highway and 
railway construction. 
Mr. Adolfsson observed that orthophotography, 
having developed considerably (as could be seen 
at the Exhibition), introduces new perspectives, 
when combined with methods of digitization. 
Mr. MacLeod said the development of digital 
maps at the Ministry of Transports in Toronto 
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provides good evidence of the usefulness of 
automated data processing, with one reservation, 
that is, that intensive use be made of it. The 
equipment may be redeemed in four years. In 
Toronto, the equipment is in operation 15 hours 
a day, on an average, and covers the scales 
between 1:10000 and 1:500. The degree of auto- 
mation in the production of maps is 10096. 
Dr. Ternryd asked whether this did not imply a 
very advanced level of training for photogram- 
metrists. 
Mr. MacLeod gave a positive answer to this, but 
added that all this was to be done only gradually. 
He said that the corresponding investments were 
justified by the reduction of costs and also by 
the data processing sub-products (D.T.M.). 
Mr. Mahan added to the preceding that all this 
was true on the condition that the accuracy was 
known (and satisfactory). Mr. Adolfsson men- 
tioned the need for recommendations for accu- 
racy of various DTM's. 
Dr. Murai observed that digital terrain models 
were of interest to almost all of the Commissions 
of the I.S.P. As a matter of fact, D.T.M. can be 
used for: 
— problems of civil engineering (transport, agri- 
culture, urban planning, industry) 
— topographical problems (stereo-pairs, gradient 
maps, perspective curves) 
— analyses of natural phenomena (sunlight, snow, 
avalanches) 
— systems embodying geographical information 
(land use, geology, etc.). 
The cartographic output can be automatically 
obtained by two different types of processes: 
the matrix processes, or point-wise (using scan- 
ners), and the sequential processes, or line-wise 
(using tracing tables). 
Dr. Kasper concluded from the audience that a 
rapid glance at the history of photogrammetry 
leads one to consider the initial task of the 
Working Group (promoting the use of photogram- 
metryin civil engineering) as completed. 
Mr MacLeod added that much remained to be 
one. 
Dr. Ternryd closed the meeting by saying that 
the area covered by the Working Group could 
be taken up once again and extended to cover 
the whole body of semi-automated photogram- 
metric methods, not only the D.T.M. 
Thursday, July 22, 1976, from 16.00 to 16.45 
Session 9 of Commission IV 
Topic: Business Meeting 
Chairman: Mr. G. Ducher (France) 
The President of the Commission read the reso- 
lutions proposed by the Resolutions Committee 
that had just held its meeting. 
After this the resolutions, five in number, were 
discussed. Resolutions 2,4 and 5 were adopted 
without modification. 
As to Resolution 1, Dr. Ternryd asked that the 
word "semi-automated" be added to the sentence 
dealing with digital models. After a general 
discussion it was decided to add a supplemen- 
tary allusion to automation to the resolution, at 
the head of the sentence containing the D.T.M. 
Then Dr. J. Zarzycki (Canada) asked that the ex- 
pression "digital topographic data base" be 
113