T11 
SUB-COMMISSION IV-I 
CADASTRAL MAPPING 
President: Mr B. Lundgren 
Secretary: Mr S. G. Möller 
  
Presentation of the General Report of Sub-Commission IV-1 
in the Meeting held on Wednesday, 7th September, 1960 
by the President, Mr Lundgren 
Because of the limited time at our disposal 
I will restrict myself exclusively to some remarks 
about our control tests in Monti di Revóira. 1 
presume that those who are interested have 
studied our printed report. Our Secretary, Mr 
Möller, who has had the heavy burden of all 
the calculations, is ready to give you any in- 
formation about the details of the work during 
the discussion at the special session. 
The principal aim of the research of Monti di 
Revóira, agreed upon in Brussels in 1958, was 
to study the accuracy of photogrammetric plot- 
ting on a large scale in mountainous terrain. 
That question has, at least preliminarily, been 
answered in a satisfactory way and our answer 
is that under the given conditions we have not 
found any remarkable difference in accuracy 
between flat and hilly terrain. There appear 
certain differences from our tables, that is true, 
but we have not found them systematical from 
a statistical point of view. Our conclusion is 
therefore — and that conclusion is in our opinion 
already confirmed in practice — that we can 
have confidence for photogrammetric methods 
also in hilly terrain. However, 1 should like to 
emphasize that this research has many limits and 
that several similar researches must be per- 
formed before we can regard our knowledge as 
complete. 
In our opinion the research of Monti di 
Revóira has actualized some other points of 
great interest. Especially I should like to com- 
ment a little on the frequency of gross errors. 
[ know that some photogrammetrists regard this 
frequency as rather extraordinary. 
The question how to avoid gross errors Is 
old in classical geodetic survey and has in most 
countries given birth to rigid rules about con- 
trols, double measurements etcetera, especially 
in cadastral survey. In photogrammetric prac- 
tice we have, in my opinion, not yet reached the 
final efficient controls which eliminate the gross 
errors and therefore we think it is necessary to 
make further efforts on that point. We really 
regret that we have not had the possibilities to 
survey the different sources of the gross errors 
and we recommend seriously that any further 
Archives 5 
controlled tests are organised in a way that such 
investigations can be made. We can only 
suppose that some of the ordinary, well-known 
sources of mistakes have influenced, for exam- 
ple, mistakes in the identification of the signals 
in the photos, mistakes by the operator when 
identifying a signal in the model, mistakes by 
the operator in reading the counter, mistakes in 
recording the co-ordinates and so on. 
Of course, many of these mistakes can be 
avoided by quite simple means. We should 
certainly be careful when comparing the organ- 
isation of a research in the ISP, when various 
parts of the work must be split up between lots 
of centres all over the world with the common 
organisation of a photogrammetric centre, re- 
sponsible for the whole procedure. Nevertheless, 
photogrammetric plotting cannot be met with 
the same confidence as geodetic until we have an 
efficient control system. We should like very 
much to hear the opinions of the many prom- 
inent experts present here, for example, if the 
determination of the co-ordinates of boundary 
points photogrammetrically can be regarded as 
quite safe without measuring the co-ordinates 
twice and by different operators. 
In Commission IV we have for the first 
time had an opportunity to compare our clas- 
sical test of accuracy with the expected accu- 
racy which can be derived from measurements 
of y-parallaxes, in particular the residual paral- 
laxes after finishing the relative and absolute 
orientation. Professor Hallert has in Commis- 
sion IV presented some very interesting inves- 
tigations about that, which in a remarkable way, 
I am convinced, have extended our theoretical 
knowledge in photogrammetry. What we should 
like to discuss is how to apply those results in 
practical work, especially if y-parallax meas- 
urements can be used for estimating the accu- 
racy of a single model. I hope we will have an 
opportunity to come back to that question in 
Commission IV-4. 
| mentioned earlier that we are fully aware 
of the many limitations of the research of 
Monti di Revóira. Let me finally tell you some 
of our experiences with regard to the organisa-