SETTING UP OF AN EXPERIMENTAL POLYGON IN ITALY, ECC. 
II 
— Diagram n° 6 : geographic coordinates and convergence of meridians. 
From the adjusted Gauss coordinates we have calculated the geographic coordi 
nates, with longitudes referring to the Rome M. Mario meridian. The Greenwich 
longitudes may be obtained from those given, by adding thereto the value I2°27'o8,"4 
The calculation results show that the mean square error of the weight unit (weight 
i has been given to each observed direction) corresponds to about 2" ; the average 
errors of coordinates are all small, their size being within the decimetre order, 
with a maximum of 27 cm on point n° 30. Also the adjustment corrections to di 
rections have generally values around 1", and only rarely arrive at 4"; in one case 
only we had a correction of 6/'5 ; on the other hand, in view of the limited size of 
the sides in question, these values are more than satisfactory. 
The accuracy of planimetrie determination therefore answered our expecta 
tions and was adequate for our aims. 
Altimetric compensation was effected by dividing the points into polygonals 
of seven or eight sides each, approximately, developing between bench marks 
of the geodetic spirit leveling lines. The closing errors of polygonals have all re 
sulted very small, and were subdvided in an inversely proportional manner to the 
squares of sides ; we further effected several checks calculating differences in height, 
by means of observed zenith distances, between points of different polygonals and 
everywhere the results agreed with the differences between the adjusted elevations 
of the same points. 
Also with regard to altimetric determinations, we can state that the precision 
arrived at was more than satisfactory. 
After completing the calculations for the basic net, we immediately started 
upon calculations to determine the additional points and the control points : as soon 
as the angle observations had been effected, they were written down on special 
forms together with the coordinates of the required known points, and transmitted 
to the Centre for Calculations and Servo-equipments » (Centro Calcoli e Servomec 
canismi) of the Engineering Faculty of the Bologna University, which then punch 
ed them onto cards, calculated them with an IBM 650 electronic computer and 
sent the results to the team dealing with ground operations. Thus operators were in a 
position immediately to check the results of their work, and whenever there were 
any mistakes, repeat their observations without losing too much time, as they 
already found themselves in the operation area. 
We applied the calculation method prepared and tested by the writer as from 
i960 : three different calculation programs marked by numbers 190, 191, 192, perform 
the calculation of planimetrie adjustment by variation of coordinates and of alti 
metric adjustment for the cases of multiple direct, mixed, or inverse intersection 
respectively. A fourth program, n° 193, provides the determination calculations by 
polar coordinates, but it has not been used in the present case. 
The programs perform the following operations : 
— calculations of reductions to the trigonometric centre, in case of out-of 
centre stations ; in view of the not too large capacity of the computer storage (1000 
words) we have not foreseen reductions to the centre for the collimated point ;