CALCULATION OF A BLOCK OF STRIPS, ETC. 
5 
Del procedimiento vienen ofrecidas dos versiones; una rigurosa, apta para el cálculo electrónico con 
las grandes calculadoras del tipo 700 y 7000 I. B. M. ; la otra expeditiva, eficaz cuando se disponga 
de a lo menos dos puntos conocidos per trozo, apta para el cálculo electrónico con las pequeñas cal 
culadoras del tipo 650 y 1620 I. B. M. Siguen aplicaciones .efectivas y ejemplos, de los que resulta 
la elevada precisión asequible. 
FOREWORD. 
1. — The classical method of setting up the problem of the block of strips 
is to limit the ground control to groups of points concentrated at the vertices or 
anyhow at the margins of the area to be surveyed. 
In practice, however, very seldom we must operate in these conditions. There 
will always be some intermediate control available, either derived from maps or 
pre-existing surveys, or created ad hoc to improve general accuracy and provide 
useful checks. 
A case of particular practical interest is when the control consists of a certain 
number of points uniformly distributed on the area to be surveyed. Though of 
a less general occurrency, this setting may be used with great profit — since a 
uniform distribution of control ensures from the very beginning a higher accuracy 
in the final results than a marginal and discontinuous distribution — in all those 
areas already provided with an efficient trigonometric detail net, created in due 
course for direct survey of maps, or for other purposes. 
2. — Such an instance is doubtlessly offered by the Italian territory, whe 
rein at present about 33,000 trig points are in existence — considering only the 
I.G.M. net and leaving out the cadastral net — with an average density of 7-8 
points every 100 km 2 and an average distance of 4-5 km from one another. In 
view of these conditions it would be absurd to apply the classical setting up of 
the block, which would ignore, or badly use, such an abundant an precious material ; 
we must therefore employ other systems based on the existing trig points, in 
their actual almost uniform distribution. 
Tha practical use is immediate. In fact, I.G.M. is since some time carrying 
out an ex-novo photogrammetric survey of the old plane-table surveys at 1:25,000 ; 
moreover, we shall very soon have to build up a large scale map (1:10,000 or 1:5,000) 
for the ever increasing technical and engineering requirements. In both cases it 
is imperative to make recourse to the more up-to-date and less expensive aero- 
photogrammetric methods, among which it seems that the block of strips, set up 
according to the above mentioned situation, may be rightly included. 
3. — Most of the European territory appears to be in a similar position ; 
as well as many extra-European countries, though with a lower density of points. 
But even in those districts which are less progressed as far as cartography is con 
cerned, and lack a good triangulation net, it might sometimes be more convenient 
to set up a continuous and uniformly distributed net than to set up groups of points 
irregularly located ; so that it seems that in the long run the method suggested 
in this paper may have a more general appliance than it might be thought.