GIUSEPPE BIRARDI 
l6 
The input data, copied by hand on a special form (see Annex 5) are punched 
onto cards. For each stretch they include : 
— a heading card, with statements and data regarding the calculation to 
be performed (including the coefficients for the sphericity correction at the scale 
of the model, and the altimetric and planimetric tolerances for the above mentioned 
automatic checks) ; 
— a certain number of cards for the known points (15 at the most) and 
for the axis points (2 at the most, with 3 references each), each showing the serial 
number of the point, the instrumental and ground coordinates ; 
— a certain number of cards for the T points (20 at the most), each showing 
the serial number of the point and the instrumental coordinates. 
The ouput data are punched onto cards. For each stretch they consist of : 
— a heading card, showing the stretch serial number, the number of T 
points, the coefficients for transformation of coordinates ; 
— as many cards as are the T points, each showing the serial number of 
the point, its instrumental coordinates, its transformed coordinates, its elevation 
except the effect of y rotation, its distance D from the stretch axis. 
Before continuing the calculation with the BL2 program, the output cards 
of the whole block are passed through a selecting machine, which sets them in 
order putting one after the other the cards concerning the same T point in the va 
rious stretches it belongs to (4 at the most) ; they are then printed out en clair. 
Thus we carry out a sight check of the coordinates from the various origins — which, 
according to the hypothesis of para. 10, should not differ so much from one another — 
in order to discover and eliminate any gross errors which may have escaped the 
preceding checks. 
c) BL2 program - it performs operations c) and d) of para. 9, i. e. the block 
calculation of the y rotation, and the consequent correction of the elevations of 
T points. 
This calculation must set up and solve the normal system deriving from ob 
servation system 4). Therefore, the T' points of any stretch must be linked with 
the corresponding T* points of the adjacent stretches (3 at the most), so as to form 
the coefficients for the observation equation relative to each coupling ; the ana 
logous coefficients for the points of known elevation must furthermore be formed. 
In view of the limited storage size of the computer at our disposal, this cannot 
be obtained from the BLi output with one only machine operation ; a series of 
successive passages is required (n - 1 in total, n being the number of stretches), 
each storing the data concerning the T l points of one stretch only. In each passage, 
the machine compares the serial number of these with the ones of adjacent stret 
ches, selects the couplings and forms the respective coefficients, whose binary 
products are accumulated in a proper storage area. Then the normal system is 
solved, and the most probable values of the y 1 rotations are calculated, by which 
the elevations of T points are corrected.