132 GRAPHICAL OR NUMERICAL PHOTOGRAMMETRY?, AUTHOR'S PRESENTATION 
, 
Author's Presentation of the Paper 
in the Meeting held on Friday, 9th September, 1960 
Mr Harry has twice mentioned this after- 
noon's subject, but not exactly in the way I have 
understood it. The subject of my paper is 
Graphical or Numerical Photogrammetry? This 
paper has been published in Photogrammetria, 
so it is not necessary to go into detail. I just want 
to remind you of a few of the main facts which 
are contained in the paper. 
There are two groups of consideration in 
making the choice between numerical and 
graphical photogrammetry. The first lies entire- 
ly in the field of the surveyor and is related to 
the question of precision and that of organisa- 
tion. 
As far as precision is concerned, I do not 
need to say very much. The efforts of the various 
sub-committees of Commission IV have given 
sufficient proof of the precision which can be 
obtained. That the graphical method is slightly 
in an unfavourable position with respect to the 
numerical one is quite clear, because you in- 
troduce there the errors in graphical presenta- 
tion. 
The second point is in relation to the cadas- 
tral surveys. In most cases cadastral surveys also 
belong to the terrain of the surveyors, so that the 
decision about what type of photogrammetry 
will be used can be said to belong entirely to the 
field of the surveyor. Here some other consid- 
erations come into the picture, especially con- 
cerned with the organisation of the work; the 
application of numerical photogrammetry opens 
the door for systemisation and mechanisation of 
the cadastral information. The instruments 
necessary for this application exist and have 
shown themselves to be available to fulfil the 
task in this respect completely. They include 
automatic registration of co-ordinates, attached 
to the restitution instrument; high-speed com- 
puters and auxiliary; equipment which is neces- 
sary to use them. In many cases, however, a 
graphical representation will be indispensable. 
Its construction may be combined with the res- 
titution instrument, but nowadays the existence 
of co-ordinate plotters makes it possible to shift 
the moment of plotting the result to another 
stage of the procedure. Also, from a technical 
point of view we may conclude that the appli- 
cation of numerical photogrammetry will match 
very nicely the demand for rationalisation of 
cadastral administrations, but there remain a 
number of problems to be solved. There is in 
the first place the economic problem, the com- 
plete set of tools for a cadaster in modern style 
which requires considerable investment. Wheth- 
er or not this is justified depends on local 
circumstances. 
A second point is the organisation of the 
work which, if carried out consequently with 
respect to an optimum efficiency, may be com- 
pletely different from the existing organisation. 
The easiest case is that you start a cadastral or- 
ganisation right from scratch so that you do not 
need to take into account existing organisation, 
but there is still another point which should not 
be forgotten: that the introduction of numerical 
photogrammetry may have consequences of a 
legal nature and in the first stage may therefore 
lead to political arguments. I am thinking here, 
for instance, about the question of the obligation 
of marking boundary points. In several coun- 
tries this exists; in others it does not. However, 
if from a technical point of view it is concluded 
that such a marking will be helpful and econom- 
ically justified, then the question arises whether 
such an application should be included in the 
law or in some other legal rule. Furthermore, 
who will pay for such a marking? 
I hope I have indicated with a lot more 
emphasis in my paper that a general answer to 
the question of whether to use graphical or 
numerical photogrammetry in a cadastral survey 
does not exist. I consider it the task of Com- 
mission IV to publish as much information as 
possible about both procedures which should 
be available to everyone who has to advise or 
make decisions in this respect; the necessary 
data which he can combine with his knowledge 
of local circumstances will enable him to come 
to a correct decision. 
The application of topographical mapping 
leads to a second group of considerations which 
have an influence on the choice of numerical or 
graphical. We can exclude aerial triangulation 
because that belongs to Commission III. 
Furthermore, from the title of my paper it is 
clear that we are dealing with large-scale or very 
large-scale mapping and not with small-scale 
mapping, because there numerical methods 
would hardly be necessary. 
For large-scale topographical maps we have 
in most cases not a purpose in itself but the maps 
are meant to help, for instance, urban planning, 
engineering projects or some other project, 
which means that such a photogrammetric 
process in general is part of a procedure which 
started probably long before the need for maps 
came up and will continue quite a time after 
  
maj 
the 
the 
moi 
resi 
tior 
fille 
the 
gra 
sen 
var 
pos 
ind 
ma 
for: 
ti01 
is t 
phi 
the 
exp 
ica 
the 
hir 
fol 
viti 
hei 
sul 
pu 
for 
rig 
yo 
co 
pir 
ea: 
by 
cei 
eri 
M 
to