revision. 
b) These results could seem to give us 
good news about revision accuracy; never- 
theless I have some doubts on this optimistic 
conclusion. In my opinion, if the original and 
the revision surveys (terrestrial or photo- 
grammetric) have the same ground accuracy, 
the accuracy of the new features reported on 
the old map is necessarily worse, due to cen- 
tering errors of the new points on the old 
ones. If we add the instability of the repro- 
duction materials, and the imperfection of the 
special simplified instruments « photos ver- 
sus map », when used, there must be an ac- 
curacy decrease. We may discuss whether it 
is significant or not ; whether it is important 
to have a standard point error of 0.4 mm in- 
stead of 0.3 mm ; if in small scale maps or 
in quick cartography of immense territories 
an error of 1 mm has some meaning or not ; 
but we must admit that each revision brings 
an accuracy decrease in the map. 
c) On the other hand we want to point 
out that only 11 Agencies (that is 29 %) do 
some accuracy checks on the revised maps, 
and that not always these checks seem to be 
effective and satisfactory. The claim of an 
unchanged accuracy after a revision seems to 
be, in many cases, rather a presumption than 
a tested ascertainment. 
In fact, some specific studies on the revi- 
sion accuracy — like the report presented by 
220 (Hungarian National Office of Lands and 
Mapping), which gives almost the same con- 
clusions as those of a study (*) which I pre- 
sented at the Paris Symposium of Commis- 
sion IV — show that in the comparison bet- 
ween a considerable number of points mea- 
sured in the sheets obtained from a precise 
photogrammetric survey and from its revi- 
sion, the mean square error of the diffe- 
rences is 0.3-0.4 mm ; which proves a notable 
accuracy worsening. 
However, we agree that such a loss is 
not so important. And we particularly agree 
with a weighty conclusion expressed by 180 
(French I.G.N.) in the « rules for total rene- 
wing»: «the degradation of the original re- 
production material is more important, to 
this purpose, than a loss of accuracy. » 
6. — The future of map revision 
a) In many Agencies (30 out of 62, 48 96) 
some studies and experiments on the revi- 
sion of maps are actually being done. Out of 
these, 7 (11 %) are concerned with the appli- 
cation of automated cartographic techniques 
to map revision; 7 (11 %) with the use of 
orthophotos or rectified photos; 3 (4 %) 
with the use of space data, space imagery, 
remote sensing ; 13 (21 96) with the improve- 
ment of ordinary photogrammetric or repro- 
duction methods and/or instrumentation (di- 
rect scribing in the field, redraft in the me- 
tric system, model orientation, simplified 
plotters and instruments, etc.). 
We already commence to see which are 
the main directions whereto the future of map 
revision is expected to move, by the use of 
automated cartographic techniques, ortho- 
photos, space information. Nevertheless, it 
must be noted that some important Agencies 
show no interest in someone of these direc- 
tions, while a great number of Agencies (32, 
i.e. 5296) are conducting no studies or expe- 
riments at all. 
b) A further indication about the future 
development lines of the revision is given by 
the answers to the item «desirable studies 
or experiments ». Here the percentage of mis- 
sing answers increases (36, i.e. 60 ?6), and this 
indicates that there is much indecision on 
this subject. Of the positive answers, 7 (10 96) 
are oriented towards automated revision 
techniques, 5 (8 96) towards the use of ortho- 
photos, 1 (2 96) towards the use of space da- 
ta, and 12 (2096) towards the improvement 
of conventional methods and devices. It is 
noteworthy that studies on cost effectiveness, 
on immediate report of field surveys, on mo- 
del orientation, on simplified instruments, on 
accuracy are deemed necessary. There is also 
080 (Canadian Topographical Survey) who 
makes us the honour of requesting a copy of 
the results arising from this Questionnaire : 
here it is, we hope it may meet their wishes. 
c) But a very precise and neat indication 
on the future of map revision is given by 
the answers to the last question « Do you 
hope that in the next years some important 
improvement in the revision area will be 
achieved ? In what sector ? ». 
Here only 27 Agencies (41 %) give no 
answer, while 3 (5 %) give a negative ans- 
wer (no improvement is to be hoped), and 
2 (396) have some doubts. But there are 34