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3 - Town planning and territorial project maps.
During the long debate that took place during the
meeting in Milano that was quoted above, almost
everybody agreed about a general Italian map at the
scale 1:10 000; Solaini was the mouthpiece (1). A
plan at such a scale is not symbolic anymore: it is
possible to reproduce it in scale.
With modem methods of analytic resection, the
uncertainty is bordered upon 1-1,5 metres both for
plan mesures and for quoted points (at least
doubled for level curves). In fact, plotting with an
analytic instrument with an internal accuracy of 5
?m, and taking in account all the other factors, we
can confine the m.s.e. point restitution in 0.1 mm
for position, and about four on ten thousand for
height: that implies the above quoted numbers.
At the moment we lack data about digital
photogrammetry applications: as known, we don't
have optoelectronic metric cameras yet (on a
plane), we normally work with scanners obtaining
the digital images from the usual analogic ones,
and from its calibration.
We believe that the 1:10.000 plan is suitable to
study the territorial planning; it is very well
"readable"; and the hardcopy printout allows the
vision for a complete province.
The Varese's one is, for example can be completely
seen from the town planners if fixed on a wall. But
we have to remember that, with suitable
enlargements on a computer screen, it is not
difficult to design planning modification.
We have to be careful, for this reason, that the
projects follow suitable techniques and we have
not to dirty the paper with various unuseful grids.
Quoting once more the meeting in Milano, most of
the audience agreed with the use of the 1:10:000
scale, at that time edited for the future Italian
Technical Plan (then replaced as known by CTR).
Among them, one of the fathers of the Italian town
planning, professor Cesare Chiodi, who taught for
a long time in our Politecnico, stated:"Plans at
1:25.000, owned by almost all European countries,
are not sufficient to an exhaustive representation of
the town planning elements..." and more "the
1:10.000 scale has the value to be sufficiently
detailed for this research and town planning project
level, and, at the same time, and it makes possible a
good vision of the subject..." (6).
Talking about the project with large pen trace, we
will quote again from Inghilleri at the meeting in
Milano: "... I have to say that, as engineer, I'm
upset with architects. I have seen many town
planning traced by felt tip pens, where the pen
thickness means 20, 30, 40 metres.
I'm not against working with the pen, but I think
that technical and economical controls are
necessary. These controls need a well done and
sufficient cartography".
As far as PRGs are concerned what more? Another
quote from Inghilleri: "...I knew,' for example, that
the town planning law states the realisation of town
planning on plans with scale 1: 10 000, and that
building plans need instead plans with scale 1: 5
000. So I asked town planners: 'What are those
plans for?' Town planners generally were not able
to answer.
They said, 'The law states this and we fit'.
We try to answer now, taking the place of the town
planners, who worked thirty years ago and,
according to our lamented colleague didn't know
the answer.
A PRG has to be drawn on a 1: 2000 scale.
The actual plan inaccuracy is twenty or thirty
centimetres in position and height, if it is, of
course, numerical and well made. No contest can
rise in the design on the ground of the lines and the
area prescriptions contained in a general town
planning, if the uncertainty is limited to these
values. If the uncertainty increases instead to one
meter and more, as in using 1: 5 000 scale, the
quarrels, even from an attorney-like point of view,
will spread.
One could opt for the same plan and scale also for
the PE, PPA and similarities, also for working on
plans with the eventual dispossession decree for
public utility or other similar process; the
communes often ask the scale 1: 500 for these
plans. We think, on the contrary, the scale 1:1000
is enough, if it is numerical and correct.
Technical present possibilities make this product
accuracy around a centimetre or just a little more.
Now, we go back to the topic of the "pen".
Even if the delimitation of the various areas of the
PRG are defined by reasonable thickness lines (but
often they use lines from 8/10 to 1 millimetre, and
at 1:2000 scale that means a ground stripe 1.6 to 2
metres wide), it is long-time tradition to identify
with some feature the same areas.
To this aim they use the most different dot and line
patterns, that strongly limit the map reading, we are
talking of the paper maps, used by professionals.
The same map that is used by the communal
technicians to trace new roads and squares and to
define construction lines.
This map is not the original, but a vulgar
reprographic copy rolled on a side and so stretched
on the other, with evident affine deformation
effects of its contents.
How to pretend then a correspondence between
such a manipulated plan and the real ground?
