SETTING UP OF AN EXPERIMENTAL POLYGON IN ITALY, ECC. 
7 
in black with a white circular border, or vice versa, according to the colouring 
of the surrounding land (fig. i). 
Fig. i - Types of markings for control points. 
Ground operations started on May 24, 1963, and were completed by September 
2, for a total of 760 operator’s days and 741 motorvehicle days. 
During the months of March and April we had prepared plans for the basic 
and additional nets ; for the net of control points we had planned a series of points 
distributed with geometrical uniformity within the area of the polygon, trying to 
choose the location of the said points on the basis of ground reconnaissance, so 
as to stray as little as possible from the planned position. 
Whilst one part of the operators proceeded with the measures for the basic 
net and the additional net, another team started on the reconnaissance operations 
and the pegging out of control points, effecting also, wherever possible, the measures 
for their determination. 
The basic net (see ann. 5) consists of 47 points, numbered consecutively from 
1 to 47 to meet the requirements of the calculation program, 44 of which were to 
be determined and 3 were of known planimetric coordinates. The coordinates of the 
latter points derive from the calculations for a triangulation net of the town of 
Florence, based on a geodetic base line measured with invar wires ; points N. 45 
and 46 are the vertices of the base net and were used to size the new net, whereas 
point N. 47 was introduced for erientation purposes. In order to improve the siz 
ing of the net, we further measured with the tellurometer the distance between 
points N. 46 and 18, which was of almost 20 km. 
Among the 47 points, 27 are located on buildings and 20 are ground points ; 
the latter were materialized by means of metals caps on concrete castings ; fur 
ther on most of the points we set a target generally consisting of a wooden pole, 
3 m long, holding three sets of tongues painted in black or white, as the case may be. 
On each point we made out a trigonometric station with a Wild T2 theodolite; 
the horizontal directions were observed according to the directions method, per 
forming six repetitions of the circle and effecting for each direction the measure 
in the two combined positions of the telescope ; the zenith distances were meas 
ured three times each, always in both telescope positions. 
The basic net was then enlarged by means of other 65 additional points each 
marked by a three figure number starting with a five. These points mostly