naire’s core, of the most direct and immediate 
interest. It includes : type of map revision 
specifically applied for each map ; production 
data (number of sheets revised per year, revi- 
sion cycle); revision procedure for each map 
type, synthetized in its general lines; accu- 
racy and checks on the revised maps; time 
comparison between revision and total rene- 
wing of the map ; 
c) future of map revision, in the mind of 
the Agency, to get an idea of the previsions, the 
hopes, the desires in the world. Here are spe- 
cified the actual studies and experiences being 
done at the Agency, those which the Agency 
deems desirable, the hoped improvements in 
a not too far future, the fields in which they 
are expected. 
It is our opinion that the information here 
collected is really precious for them who work 
in the operative field, and not only as far as 
revision is concerned. To know the name, the 
address, the main production lines of the 
most important cartographic Agencies in the 
world has a real and tangible practical utility, 
even only for the sake of study, of compari- 
son, of incentive. 
It is a pity that many Countries and Agen- 
cies could not send their answers to the Ques- 
tionnaire, certainly not for lack of will or of 
capacity. However, I must say that in compa- 
rison with the answers of some firms, merely 
commercial, it is preferable no answer at all. 
II - THE INTERPRETATION OF INFORMA- 
TION 
4. - From the body of the collected infor- 
mation and data it comes out some result of 
a general character, whose interest is really 
noteworthy. We shall try to point it out, em- 
phasizing its most significant aspects and 
adding some comment; but in our opinion 
the best comment will be the one which eve- 
ryone will do on his own account, by exami- 
ning the complete table of the answers; in 
fact, this is the reason why we have published 
them. 
5. - General character remarks. 
a) The answers which we received deal 
with a very large amount of situations in diffe- 
rent countries and territories, which go from 
the updating of 1 : 500000 and 1 : 250000 
scale maps of immense territories (like Aus- 
tralia and Argentina) to the revision of 
1:1000 and 1 : 2000 scale town plans (like 
Vienna). 
Now, we must 
point out that in the generality of the cases, 
except some Countries of very high technolo- 
gical development, there is not a well defined 
revision policy, nor a consistent and precise 
planning for it. The revision of the maps is 
generally done when there is the possibility 
to do it (when new photo coverages are avai- 
lable, or when personnel and facilities are 
not differently engaged, etc.), or when it be- 
comes compul sory because of the map obso- 
lescence and the users’ protests. 
In our opinion, this must not be regarded 
as a discouraging note. Maybe it is a sign of 
the tremendous difficulty of the revision pro- 
blem, and of the cartographic problem in ge- 
neral, as in many Countries the basic mapping 
is not yet completed, and in some others it is 
not started at all. It is anyhow an indication 
that something must be done for a more effi- 
cient solution of the revision problem. 
b) The frequency of the revision types 
employed in the cases which result from the 
answers we received is reported in the follo- 
wing Table I. As you can see, the revision ty- 
pes C2 (complete, cyclic) and C3 (complete, 
selective) are the most largely employed for 
any map types for medium and little scale 
maps (Nos 3, 4, 5, 6) the revision type A3 
(quick, selective) is largely employed. Partial 
revisions (B1, B2, B3) are scarcely employed 
for any map type; in fact it is not frequent 
the case that only a preselected part of a map 
must be updated. Quick revisions are a mino- 
rity in comparison with complete revisions, 
but in the field of medium scale maps (map 
types Nos 3, 4) the difference is not so rele- 
vant : in my opinion that is because in many 
cases a revision limited to highways, impor- 
tant roads, important buildings, new lay-outs 
of towns, etc., gives quickly what users really 
want. 
As typical examples of the extreme cases 
of revision types we will mention 021 (Argen- 
tina, Military Geographic Institute), where 
the revision is done only in the small scales 
(1 : 250 000 and smaller), utilizing information 
from any source (including space imagery) di- 
rectly transferred onto the map guides without 
any regular photogrammetric plotting ; and 
160 (United Kingdom, Ordnance Survey), 
3